I think you are correct in that Draco is meant to be a site to hold the qualities she finds most obnoxious and angering in people. And yeah, I don't know if she hates him so much as what he represents. But she has shown that she can give other characters more than one side: Sirius was very likeable, but flawed in that he was hot-tempered, prone to acting before thinking, and extremely cruel toward Snape in particular; Harry's folks were also not the perfect people he idolized them as; Dumbledore was the all-knowing god until book five, when she made it clear that he is not perfect, not all-powerful, and that he does make mistakes like everyone else; and Harry, for all his childish innocence and naivete, has taken on a very dark disorienting thread, is argumentative, furious, and capable of hatred (something she has not really allowed for him until this point). So it gives me a little hope that she may address more of her 2-D characters in this way. But I wonder if I am not hoping for too much from her.