(Posting this not because "my opinions are so important", but because I saw many people saying that "no one here supports JK Rowling.)
Because she has courage.
I don't agree with her on everything. But I'd rather have someone who doesn't agree with me, but who has courage, than a pathetic coward who agrees with me on everything. How bad would that make me look?
I feel the same way about Roger Waters. Like Paul Joseph Watson said:
You have to respect Roger Waters. Don't agree with him on a lot, but he could have safely retired with his massive pile of money and had a quiet life. Instead, he's 79 and is still a constant irritant to the regime. Few such cases. source
Be an irritant to the regime.
JK Rowling is in absolutely no way an irritant to the regime, the only people against her are screeching troons on twitter and resetera and the like. She's in no danger of losing anything at all.