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.