I see two possibilities:

Possibility A: they care about the feelings of fictional characters who they can control more than the feelings of real people with their own ideas.

Possibility B: Misogyny and transphobia since the majority of fandom participation is from women and trans men. Men are allowed to have interests as adults, women are supposed to be Mothers and nothing else.

Especially considering how much anti rhetoric dovetails with and mirrors terf rhetoric.

Probably a little of both.