Along these lines, CGP Grey's video about Anger Thought Germs is an excellent breakdown of why anger spreads like nothing else:
https://www.youtube.com/watch?v=rE3j_RHkqJc
You combine that behavior with social media, especially Twitter, and the symbiotic relationship with the news media. It's a non-stop anger generation machine. Rapidly iterating on these thoughts, packaging and surfacing the most potent, viral version. Any nuance and context long ago removed.
https://slatestarcodex.com/2014/12/17/the-toxoplasma-of-rage...
The summary is that controversial issues are the ones that go viral. Not the ones that necessarily deserve to go viral. That is the theory of the post I linked -- I do not make any commentary whatsoever about any individual event.