this is "nightline." >> tonight, facebook face-off. mark zuckerberg's very public apology about your privacy. >> we didn't take a broad enough view of our responsibility, and that was a big mistake. and it was my mistake. and i'm sorry. >> tough questions hanging over the young billionaire. >> how is today's apology different, and why should we trust facebook to make the necessarily changes to ensure user privacy? >> but can he make his case and promise enough changes to save facebook as we know it? plus, re-righting history. katie couric looks at issues marking the stark divide in our country. >> i was marching with the confederate flag on my back for three years.

>> how did we get here? >> we were so blind to it, honestly. >> and how do we move forward? but first the "nightline 5." >> at pro plan we believe nutrition is full of possibilities to improve your pet's life. we're redefining what nutrition can do. because the possibility of a longer life and a better life is the greatest possibility of all. purina pro plan. nutrition that performs. ♪ ♪ only tylenol rapid release gels have laser-drilled holes that release medicine fast for fast pain relief. tylenol. >> number one coming up in just

good evening and thank you for joining us. we start here with a trial by fire for mark zuckerberg who

started facebook in his dorm room and built it into a company at the center of american life. and now at the center of enormous controversy over everything from russian meddling to the privacy of your personal information. he was hauled before congress today and it got contentious at times. abc's mary bruce was right there. >> are users actually safe? is facebook being safe? >> senator, i think facebook is safe. i use it, my family use it, all the people i love and care about use it all the time. >> why should we trust facebook to make the necessary change in this. >> we have made a lot of mistakes. >> do you think the average consumer understands what they're signing up for? >> i don't think the average person likely reads that whole document. >> the facebook founder and ceo taking the hot seat for the first time, facing tough questions from over 40 u.s. senators. one of the primary concerns, facebook's growing role in our elections. >> what is facebook doing to prevent foreign actors from

interfering in u.s. elections? >> one of my top priorities in 2018 is to get this right. my my greatest regrets in running the company is that we were slow in identifying the russian information operations in 2016. we expected them to do a number of more traditional signer attacks, which we did identify and notify the campaigns they were trying to hack into them, we were slow identifying the new type of information operations. >> reporter: swapping out his signature gray t-shirt and jeans for a suit, zuckerberg remained stoic, sitting calmly for nearly five hours. >> we've seen the apology tours before. >> your user agreement sucks. >> reporter: the two days of congressional hearings called as a result of that controversial cambridge analytica data breach. >> is facebook keeping track of your phone calls and your text messages? >> reporter: many questioning whether their information is truly safe on the social network. >> cambridge analytica reportedly breached the profiles of tens of millions of users --

>> reporter: the millennial billionaire first arrived in washington on monday, meeting privately with lawmakers and dodging questions from reporters. >> mr. zuckerberg, are you doing enough to protect your users? >> reporter: this week, 87 million facebook users are receiving a notice on their feeds informing them their personal data was shared with the political consulting firm. during the hearing, zuckerberg took personal responsibility for the social network's failure to safe guard users' privacy. >> that was a big mistake and it was my mistake and i'm sorry. i started facebook, i run it, and i'm responsible for what happens here. >> i think mark zuckerberg's going to sleep a lot better tonight than last night. he came in sounding well prepared, knowledgeable. he certainly owned up to his mistakes, which is an important thing to do. >> reporter: zuckerberg admitting facebook has been used to spread fake news and hate speech. >> it's clear now that we didn't do enough to prevent these tools from being used for harm as well. >> there are a great many

americans who i think are deeply concerned that facebook and other tech companies are engaged in a pervasive pattern of bias and political censorship. there have been numerous instances with facebook, may of 2016 gizmoto said facebook routinely suppressed conservative stories from trending news, including stories about mitt romney, including stories about glenn beck, to a great many americans that appears to be a pervasive pattern of political bias. do you agree with that assessment? >> senator, let me say a few things about this. first, i understand where that concern is coming from, because facebook and the tech industry are located in silicon valley which is an extremely left-leaning place. this is actually a concern that i have and that i try to root out. the company is making sure that we don't have any bias in the work that we do. and i think it is a fair concern. there are people in russia whose job it is to try to exploit our

systems and other internet systems and other systems as well. this is an arms race. they're going to keep on getting better at this, and we need to invest in keeping on getting better at this too. >> reporter: last year facebook estimated that 146 million americans saw russian-linked content during the election. lawmakers blasted the company for not doing more to stop it. saying that companies like his had been given too much liberty and need to be regulated. >> i come in peace. i don't want to vote to have to regulate facebook. but by god, i will. a lot of that depends on you. >> reporter: zuckerberg also admits that starting the company at such a young age may have led to its imperfections. >> it's pretty much impossible, i believe, to start a company in your dorm room and then grow it to be at the scale that we're at now without making some mistakes. >> reporter: the entrepreneur was just 20 years old when he and college friends built the first facebook. >> your actions could permanently destroy everything i've been working on -- >> we've been working on. >> reporter: the drama behind facebook's development high

heated in the academy award-winning film "the social network." >> i'm not talking about a dating site, i'm talking about taking the entire social experience of college and putting it online. >> reporter: facebook is now ubiquitous world wide. with more than 2 billion users logging on each month, sharing everything from photos to status updates, where they work, even their religious and political beliefs. with that growing number, there are increasing concerns about who has access to a user's personal information. >> one of the threats with your data on facebook is your phone number. it might have been scraped by scammers who want to use your information to spam you or steal your identity. >> reporter: part of the problem may be built in. >> how do you sustain a business model in which users don't pay for your service? >> we run ads. >> reporter: facebook makes billions by selling ads based on all the data they're collecting. in 2017 the company boasted revenues of a whopping $40.7 billion. earlier this month, facebook's chief operating officer, sheryl

sandberg -- >> it was information people had already listed on facebook publicly. now, that doesn't make it okay -- >> reporter: she pointed out that facebook is free, and suggested users may need to pay to stop facebook from collecting and using their data to sell ads. >> are you actually considering having facebook users pay for you not to use that information? >> senator, people have a control over how their information is used in ads in the product today. i think what cheryl was saying was that in order to not run ads at all, we would still need some sort of business model. >> i actually might be willing to pay. i'd like to know, there is a number that you will totally protect my privacy, not use my information for any advertising, any personally targeted stuff at all? what's the price? i'd like to know that price. >> reporter: concerned, apple cofounder steve wozniak announced he's deactivating his facebook account, joining the

"delete facebook" movement. >> it hit a breaking point for me. >> reporter: last month it was facebook in the crosshairs of its own data breach. >> if you are looking at trying to create information weapons, the battle space that you operate in is social media. that is where the fight happens. >> reporter: chris wily worked at cambridge analytica, a consulting firm which helps political candidates better target voters online. wily claims in summer 2014 cambridge analytica used a third-party to take data from the facebook accounts of roughly 87 million americans. >> weaponizing the internet. >> weaponizing the internet, absolutely. >> reporter: two years later, cambridge analytica went on to work for the trump campaign but says it never used that data in question. the campaign itself denies using cambridge analytica saying it relied on information from the rnc. cambridge analytica has denied any wrongdoing. >> why didn't facebook ban

cambridge in 2015? why did you wait? >> senator, this is clearly one of the questions that i asked our team as soon as i learned about this, why did we wait until we found out about the reports last month to ban them? >> reporter: but for those whose data has already been compromised, the breach may have far-reaching consequences. right before zuckerberg appeared on capitol hill, facebook and cambridge analytica were hit with a class action lawsuit accusing the company of misusing personal information. >> it's unlikely people will stop using facebook. the social network has become a utility. it not only owns facebook, it owns instagram, what's up, and a number of other companies. >> reporter: the social media site says it's doubling down on security, increasing the number of employees working on security from 10,000 to 20,000. zuckerberg's calm, careful, and contrite demeanor played well. facebook stock increased 4.5%. >> i think mark zuckerberg is comfortable being mark zuckerberg. i believe facebook is the canary in the coal mine.

they're the biggest, so they're obviously going to get the most scrutiny. >> the hearing is adjourned. >> reporter: for "nightline," i'm mary bruce in washington. next here, how we depict the history of race in america has boiled over on one of america's most prestigious universitys. katie couric takes us inside in a preview of the new series "america inside out." with the power of 335 turbo-charged horses lincoln mkx, more horsepower than the lexus rx350 and a quiet interior from which to admire them. the lincoln spring sales event is here. for a limited time get zero percent apr on the lincoln mkx. hurry in today to your lincoln dealer. with recurring constipation and belly pain if you feel like you spend too much time in the bathroom talk to your doctor and say yesss! to linzess.

♪ yesss! linzess treats adults with ibs with constipation or chronic constipation. linzess can help relieve your belly pain, and lets you have more frequent and complete bowel movements. linzess is not a laxative. it works differently to help you get ahead of your recurring constipation and belly pain. do not give linzess to children less than 6, and it should not be given to children 6 to less than 18. it may harm them. do not take linzess if you have a bowel blockage. get immediate help if you develop unusual or severe stomach pain, especially with bloody or black stools. the most common side effect is diarrhea, sometimes severe. if it's severe, stop taking linzess and call your doctor right away. other side effects include gas, stomach area pain, and swelling. so say yesss! to help for recurring constipation. yesss! to help for belly pain. talk to your doctor and say yesss! linzess.

advil liqui-gels minis. breakthrough in pain relief. a mighty small pill with concentrated power that works at liquid speed. you'll ask... what pain? advil liqui-gels minis. ♪ ♪ ♪ raindrops on roses and whiskers on kittens ♪ ♪ bright copper kettles and warm woolen mittens ♪ ♪ brown paper packages tied up with strings ♪ ♪ these are a few of my favorite things ♪ ♪ ♪

always one of america's most painful issues, has really come to a boil. from the streets of charlottesville to college campuses.

tonight, katie couric gives us a preview of her new documentary examining the battle over statues and school names and how we can better come to terms with the darkest chapters of our past. >> reporter: last august, something terrifying happened in charlottesville, virginia. white nationalists descended on this normally quiet college town. >> fights are breaking out. >> reporter: it was one of the most prominent displays of hate this country has seen in decades. >> they had riot gear and they charged us is what happened. >> reporter: as i watched the violence unfold, i wondered, how did we get here? >> here come the supremacists. >> reporter: what's behind this war? >> scary, isn't it? makes me want to cry. >> yes. >> reporter: it was hard to believe the match that ignited

this was the statue of robert e. lee. from charlottesville to new orleans, from high school football fields to college campuses, there are more than 650 confederate monuments across the country. 85 schools and 80 counties and cities are named after prominent confederate figures. >> we have a right to our heritage and traditions as much as anyone else. >> reporter: i set out to understand this battle over history. how we commemorate the past -- >> i was marching with a confederate flag on my back for three years. >> we were so blind to it, honestly. >> reporter: and what it says about us today. are we rewriting history? or re-righting it? some statues of confederate heroes be removed, in your view? >> reporter: if the battle over monuments has been raging in

towns across the country, the early skirmishes started at ivy league universities like yale. >> hey, hey, ho, ho -- >> reporter: calhoun college was named in 1933 after yale alumnus john c. calhoun, a senator from south carolina who later served as vice president to john adams and andrew jackson. but that's not all. >> the first half of the 19th century, he was the most strident articulator, to use his words, of slavery as a positive good. and he rooted that view that slavery was a positive both for slaveholders and slaves. an idea that i think is deeply disturbing to us today. he rooted that belief in core

beliefs about white supremacy. >> reporter: senior deja moore said calhoun's name and images from his time made her uncomfortable, especially in the dining hall. >> right across from me i can see the stained glass window that depicts two slaves picking something. it's a symbol that declares, you do not belong here. or you are imagined in this space to fulfill a certain really limited role. >> reporter: the already-simmering debate became more heated after yale dining hall worker corey menefee smashed one of the windows. >> although university worker for eight years, menefee says he had been working in the dining hall at calhoun college for just six months. while mopping floors the 38-year-old took a mop handle to the subject of his disgust. >> what was going through your head, corey? >> i was just sick of looking at that window. here we are in the 21st century.

and i don't think those type of images should be blatantly displayed in places like dining halls. it's culturally insensitive. it's no secret that the majority of the employees who work in the dining hall are of african-american department. >> reporter: it was a literal and figuretive breaking point. >> take down these racist window panes! >> reporter: the yale president was initially opposed to changing the name. >> our campus, both in the classroom but also outside of the classroom, is a living history lesson. and i wanted to make sure that that conversation about calhoun was one that we could always have. >> change the name! >> reporter: he was caught between students who thought his decision was wrong-headed and older alumni who felt he should stand on the side of tradition.

he appointed a committee to come up with a blueprint for who stays and who goes. after all, nine other buildings on campus are named for men associated with slavery. including mr. yale himself. john wit was the head of the committee. >> on a university campus like ours renaming is rare but might be appropriate. principal legacies, thingt whether the idea was contested at the time of the namesake, thinking about what the motive of the university was in putting the name on the building, and how does the building work in helping to build community? >> reporter: the committee came up with four principles and discovered calhoun's name was controversial even back in 1933. >> there were statements written at the time saying, really? john c. calhoun? >> reporter: so at a ceremony in the fall, calhoun college was officially renamed after the late navy admiral, computer

pioneer, and yale alumna, grace hopper. >> lest those that belong to this college now, grace murray harper is your home -- >> was it emotional for you in there? >> it was. i got hit with the emotion right before i walked in. and it was just pure joy. >> changing the people that we honor helps a wider range of students be able to envision themselves as someone who can make a difference, who will be remembered. >> reporter: as part of a conscious effort to not sanitize or erase the past, calhoun's name and image will remain on the edifice. >> it's no longer the name by which this college is known. but the history and what we need to learn from and about john c. calhoun is not wiped away. >> we can't forget that yale was a university that once did have a college, a very important part

of the campus, dedicated to john c. calhoun. >> reporter: for "nightline," i'm katie couric. >> our thanks to katie. and "america inside out with katie couric" premieres tomorrow night on the national geographic channel. that you don't think about is very much. counties it's really not very important. i was in the stone ages as much as technology wise. and i would say i had nothing. you become a school teacher for one reason, you love kids. and so you don't have the same tools, you don't always believe you have the same... outcomes achievable for yourself.

when we got the tablets, it changed everything. by giving them that technology and then marrying it with a curriculum that's designed to have technology at the heart of it, we are really changing the way that students learn. and i can't wait for ten years from now when i get to talk to them again and see, like, who they are. ♪ depend silhouette active fit briefs, feature a thin design for complete comfort. they say "move it or lose it" and at my age, i'm moving more than ever. because getting older is inevitable. but feeling older? that's something i control. get a coupon at depend.com

♪

♪ get high speed internet from at&t. $30 per month. no extra monthly fees. more for your thing. that's our thing. visit att.com/internet.

finally tonight, a swing and a miss. a "wheel of fortune" contestant is out thousands of dollars for a simple mispronunciation. this contestant about to solve the puzzle, all he had to do was read the phrase correctly. >> flamingo dance lessons.

sorry. i was nervous, i've never been on national tv before, it was crazy. and slip of the tongue, literally. >> his mispronunciation of "flamenco dance lessons" cost him 7 huh bucks and a trip to spain. don't feel bad, he walked away with over $19,000. one vowel and one consonant away from a trip to spain. thank you for watching "nightline." as always, we're online 24/7 on our "nightline" facebook page. it's just my eczema again,t. but it's fine. yeah, it's fine. you ok? eczema. it's fine.

hey! hi! aren't you hot? eczema again? it's fine. i saw something the other day. eczema exposed. your eczema could be something called atopic dermatitis, which can be caused by inflammation under your skin. maybe you should ask your doctor? go to eczemaexposed.com to learn more.