It’s a core human weakness that goes by many names, “false dichotomy”, “black or white thinking”, “for us or against us”, etc. etc.

Humans have trouble with nuance on any issue that has emotional impact for them.

The standard scenario is team A says mean things about team B. People with a connection to team B are insulted, as they should be. Some some grifter comes along and says extra mean things about team A. The wounded of team B exalt the grifter giving them the attention that they crave. Some grifter on team A will do the same. And both sides, full of the wounded, slide deeper and deeper into hateful manias.

If you take a step back, zoom out a bit, it is quite clear that both teams have, have spiraled into a hateful mania. This happens all the time, and it is our job, as rational, caring human beings, to not participate in or support any of the hate.