I think what really winds them up - beyond the usual misogyny - is the fact that she's not just rich, she's so mind bogglingly, in your face, fuck you rich that she never ever has to work again, that even if she did never work again she'd still be earning more money than she knows how to spend through royalties, and that's what gives her the power to speak up against this. Because nearly everyone else has a mortgage and bills to pay and they just can't afford to lose their livelihood by pointing out that the emperor is stark bollock naked.
And then to add insult to injury, not only will she not fucking shut up and they cannot make her fucking shut up, but she's still writing books and having her work adapted into films and TV series and computer games and people are still fucking buying them. Why are people still fucking buying her work? Haven't they got the message?
Even thirty something non binary millennials who are you to their eyeballs in preferred pronouns are still fucking buying Hogwarts Legacy and then making apologetic donations to trans charities to try and offset their terrible crimes because they love Harry Potter so much.
No wonder the trans activists are fucking raging. She's unsilenceable and uncancellable.
Ironically I think the fact that these American 35 year old babies sheep millennials love Harry Potter so much contributes to the amount of slagging off they do. Because they know they'll be social pariahs if they don't hate JK Rowling but they still love Potter, so they have to say, "Obviously JK Rowling is a hateful bigot and I'm so disappointed that she turned out to be Voldemort" in some public act of verbal self-flaggelation before they're allowed to continue to enjoy Potter.
I mean, they could just fucking grow up and find some new books, but there we have it.