Boaz Hameiri of the Annenberg School for Communication spoke about a study he conducted in 2014. He and his co-author found that “extreme rhetoric can lead some people to pull back from the brink” of extremism. However, if extreme messaging is normalized in political debate, its moderating effect is weakened.
https://www.washingtonpost.com/politics/in-america-talk-turns-to-something-unspoken-for-150-years-civil-war/2019/02/28/b3733af8-3ae4-11e9-a2cd-307b06d0257b_story.html The Washington Post