she is basically the platonic ideal of a certain kind of middle-class white liberal - well-meaning, kind, but ignorant and unwilling to learn

This is how I see her as well. It's not malice as much as ignorance, but because she is such a prominent and powerful public figure, her ignorance can cause a lot of damage. She's a lot like Joss Whedon, I think: they were both praised for their progressiveness and hailed as feminist heroes, and I think JKR like Whedon started to believe her own hype, becoming totally ignorant of her own flaws and prejudices.

(the "I am a good person. Good people don't do bad things. Therefore everything I do is good." fallacy)