. >> reporter: psychologist peter coleman runs columbia university's center for cooperation and confliction. so how bad is polarization in america, peter, compared to the past? >> it's bad, i mean, jon meacham, the historian, has compared today as being similar to where america was in the 1850s right before the us civil war. >> reporter: coleman's r.x. is detailed in a recent book, "the way out," which begins with a fatal 1994 shooting rampage at two abortion clinicsutside boston. in the wake of that tragedy, activists on both sides of the issue agreed to meet. of the pro-choice activists? >> hard and harsh and angry. >> reporter: pro-choice episcopal priest anne fowler's image of pro-life advocates? >> not thoughtful. not deep. >> reporter: and says peter coleman... >> they still remain opposed to one another on the issue of abortion, on pro-life, pro- choice, but they developed affection for one another in relationships that were thick and important. and ultimately, they changed the probabilities around violence in america on this issue. >> reporter: no changed minds, however. does tha