It's a paradox. I generally have nothing against them, but I've heard criminal defense lawyers defend their profession by pointing out the sacrifice they're making, associating themselves with criminals, being despised themselves for defending certain people while doing a job without which the legal system couldn't function. We should respect them for that. But----if we respect them for being despised, then they aren't despised, they're respected, in which case we have nothing to respect them for.
It's like that with Fred Phelps. He's the now-dead guy who would picket funerals with signs that say "God hates fags". There are some people, including a gay activist I wrote about in another entry, who say not to hate Phelps, don't celebrate his death, because he ultimately benefited the cause of gay rights by being so vile that people felt only sympathy for his victims. But----he only benefited gays by being universally hated, so if we don't hate him, that would negate the one thing there is to not hate him for.
I say don't try to be clever. If someone's a horrible person, feel free to hate him.