I think that there are different levels of
hate, just as there exists different levels of
love. There's the "I hate green beans" sort of hate, hate that applies because you dislike something and hate fits better in the sentence, though if you sat down and thought about it, hate is rather strong, eh? Another level is hating a person who is prominant in the public or historical
domain (or who you don't know on a personal level, but know of) for an action they have taken that you believe hurts you or others. For example, hating
Hitler because he was a general all-around bad guy who killed a bunch of people. Though this level of hate can be very damaging (such as the case with
hate crimes), but not the highest level of hate.
True hate, in my opinion, is deep, personal hatred, and I believe that it stems from one emotion: hurt. Love and hate are related, you have to love someone somewhere in your mind before you can hate them, and hate stems from having someone that you love hurt you horribly.
Hate is love distorted and reflected back.