I think he missed a couple of triggers that really set the TRAs off with JKR.
It's not just that she's unequivocally a woman and they're not so convinced about themselves; she's a woman with power and position that she achieved by her own hard work, talent and determination, meaning she's above being sacked or cancelled; their usual route of attack. Above even that, she's a woman with a clear, logical, articulate voice that they cannot silence, and she never gets down to their level and screams abuse back.
The person who keeps their temper, maintains courtesy and deals in facts is the antithesis of the Twitter mob. She's untouchable and they can't stand it. 🤷🏼♀️