Google brings up a lot of articles saying JKR is transphobic, but no actual articles of her being transphobic.
This is only part of her essay where she mentions trans women being allowed in women's spaces, and the way I read it is that she doesn't think transwomen are a danger to women. But that men will take advantage of self ID. And we know they will. Because they have.
I believe the majority of trans-identified people not only pose zero threat to others, but are vulnerable for all the reasons I’ve outlined. Trans people need and deserve protection. Like women, they’re most likely to be killed by sexual partners. Trans women who work in the sex industry, particularly trans women of colour, are at particular risk. Like every other domestic abuse and sexual assault survivor I know, I feel nothing but empathy and solidarity with trans women who’ve been abused by men.
So I want trans women to be safe. At the same time, I do not want to make natal girls and women less safe. When you throw open the doors of bathrooms and changing rooms to any man who believes or feels he’s a woman – and, as I’ve said, gender confirmation certificates may now be granted without any need for surgery or hormones – then you open the door to any and all men who wish to come inside. That is the simple truth.
Oh and yes, she does refer the the "majority of trans identified people" rather than saying all trans identified people. But that's no different imo to me saying most men aren't rapists. But some are.
Any one who wants me to be on "their side" needs to provide evidence as to why. At the moment I'm on JKRs side. If anyone can provide evidence that I'm wrong then I'll hold my hands up.