@wavedancer99
The sentence you have quoted is from JKR's essay but makes a lot more sense in context. I'll quote the entire paragraph it comes from -
'But endlessly unpleasant as its constant targeting of me has been, I refuse to bow down to a movement that I believe is doing demonstrable harm in seeking to erode ‘woman’ as a political and biological class and offering cover to predators like few before it. I stand alongside the brave women and men, gay, straight and trans, who’re standing up for freedom of speech and thought, and for the rights and safety of some of the most vulnerable in our society: young gay kids, fragile teenagers, and women who’re reliant on and wish to retain their single sex spaces. Polls show those women are in the vast majority, and exclude only those privileged or lucky enough never to have come up against male violence or sexual assault, and who’ve never troubled to educate themselves on how prevalent it is.'
She is referring to self ID. The predators she refers to are the people (however they identify) who will take advantage of self ID. She states it explicitly earlier in her essay-
'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.'
I mean, you'll know that having read the essay? You're not just relying on quotes on Twitter surely?