Yes this is one of the funniest things about Rowling, she used JK because she thought the books would be more popular with an ambigious name that wasn’t gendered, she also writes under a male pseudonym.
The best part is that she opposes all kinds of gender affirming surgery, even for adults, despite the mountains of plastic surgery she has done on her face. What’s that if not gender affirming surgery?
There’s plenty more I could say, because Joanne is also incredibly lazy with her writing when it comes to diversity (see Kingsley Shacklebolt, Cho Chang), and her books are incredibly dedicated to maintaining the status quo and not improving things for the underprivileged. But the more obvious examples of bigotry, off the top of my head, are:
Slavery isn’t that bad actually: Hermione is characterised as an SJW for caring about the slavery of house elves, the house elves like being slaves and are happier being slaves except for Dobby. One of them even falls into alcoholism (wonder where she got that from)? Rowling later wrote an essay defending this choice.
(Also, instead of freeing his slave at the end of the books, Harry talks about how much he wants his slave to make him a sandwich.)
Antisemitism: Jewish stereotypes with the goblins. Need I say more?
Transphobia even back then for women who don’t conform to beauty standards: Rita Skeeter’s features are described as “mannish” and her appearance is insulted along these lines on multiple occasions.
Fatphobia: evil characters are the size of “small killer whales” and are “pigs” while good characters are “plump” and “chubby”.
Child abuse for the greater good: Dumbledore leaving Harry with the Dursleys is fucking mental.