There is a lot of evidence that much comes from powerful parties such as governments and political actors, who seek to promote conflict, division, and/or the far right (EDIT: and others too, but the far right seems especially prominent). For example, one report I read said that the Russia government's Facebook activity for the 2016 U.S. election focused "overwhelmingly" on race,[0] and recently I read that Russian government Twitter bots sent thousands of tweets criticizing NFL anthem protestors.[1] I'm going to try to find the links and add them. (None of this is surprising: During the Cold War the Soviets tried to aggravate U.S. racial division; for example, a former officer said that they would send racist hate mail to African-American leaders, then 'leak' to the press that the leaders had received hate mail.)
The real question is how powerful the technology is. How effectively can you manipulate public opinion? I hardly see that issue discussed.
[0] https://eu.usatoday.com/story/news/2018/05/11/what-we-found-... More coverage: https://www.theguardian.com/technology/2017/oct/30/facebook-...
[1] https://www.si.com/nfl/2018/10/22/russian-twitter-trolls-nfl... which links to https://www.wsj.com/articles/how-russian-trolls-inflamed-nfl...
EDIT: Minor edits to make my comments more consistent with the citations.