One of the curious/interesting things I've seen is the smoothing out of Rowling - that is, a consistent attitude to her that places her, naturally, on a teleology: she is anti-trans, therefore she is anti-semitic (due to the goblins), therefore she is one step away from full fash. Any day now, she'll manifest in her true form.
I suspect in many cases that IS a pretty consistent through-line: prejudice breds prejudice, etc. But surely not in all? I'm not particularly interested in defending Rowling or not, nor in the goblin thing (which strikes me as a persistent, widely-based trope, and to make it a sign of Rowling's distinct 'evil' is a stretch), but I am interested in the need for her to be 'just on the cusp' of being the ultimate satan, the fash.
I think part of this plays on a general contempt for liberalism in online culture. That is, there's a lot of sympathy for more radical trains of thought (yet a distinct lack of radical participation, speaking broadly across society), and liberalism is seen - certainly by the committed - as a de facto enabler of fascism etc. It's a very well-worn story that only has so much play, historically. See also: centrist dads, 'milquetoast' commentators, etc. Thus Rowling's clear moral message in Harry Potter - that Nazis are bad, OK - is taken as a sop, rather than anything meaningful (and sure, it does have numerous thematic oddities and gaps, such as the elves), because Rowling says things that other people vehemently disagree with. Ergo her politics are entirely suspect; thus one cannot be flawed and mistaken, one must be evil.
None of this is to say I actually agree with Rowling on anything: her morals in HP seem... OK? If not particularly interesting, and there are some bits like the elves that are handled very peculiarly given the logic of the heroes themselves. As for trans issues, I can't see any other position being viable than arguing for their rights as humans, first and foremost. It just strikes me that each 'side' in this argument has a story it NEEDS her to play a role in.