Same as with politics.

People make something stupid (and usually toxic) the center of their identity, and develop a parasocial obsession with it due to having nothing going on in their own lives and want to latch onto someone elses success.. especially if that someone else displays the same unhealthy/bad traits that they personally have and identify with, to the point that any threat to, or criticism against, their idol, is seen as the most egregious of personal attacks on them as a person. So they strike out as if they've been personally done the worst wrong imaginable.

We like to think we’re evolved, but ultimately we’re still tribal creatures. It’s just that the tribes are a bit wider these days.

I forget the name of the bias/fallacy, but it's something like "I love and support X. If X is bad, then I support something bad, then I'm bad. Since I'm a good person, and I support X, then X must be good or I wouldn't support them"

It's probably a quirk of how we make decisions - we don't consciously make decisions. Instead, we might weigh out the options and that affects our choice, but in the moment we choose subconsciously. It might feel like we made a decision consciously, but sometimes at the last second we deviate from the course we chose (or upon choosing, realize that despite our thoughts we actually have already made up our mind otherwise)... Then we have to rationalize that choice, or start down a long and challenging road of constant introspection