we're all up all "nightline" with james lowman. >> reporter: this ultra conservative rhetoric now seepingut to the fringes and into the mainstream, following the migration crisis has been a resurgence if right wing thought. >> this is the culture we have here. we don't have an islam culture here. >> reporter: to packed stadiums in france, scrambling to regain what their country is losing. the traditional identity, culture, their heritage. that message amplified with a click of a button, when president trump tweeted a string of inflammatory videos, purporting to show violence committed by muslims. the three videos originally shared by an anti-islam group called britain first. but condemnation came swiftly. >> britain first is a hateful organization. >> reporter: and it turned out the attacker in this video wasn't a muslim immigrant at all but was double. yet the white house doubled down, denying the president was pushing anti-muslim propaganda. >> look, i'm not talking about the nature of the video. i think you're focussing on the wrong thing. >> reporter: instead, making a case for nation