I agree with Naturallytanned, some people do such evil things mainly to ones they think wont retaliate. Underestimate can be the reason for hate. Just like bullies who are now getting ran over by cars and shot by smaller ones they didn't expect. Evil begets evil hate begets hate violence begets violence. Ignorance is not always the case sometimes people understand exactly what's going on and can't stand it.
Hate seems to fall into 3 categories: 1.) Fear and misunderstanding 2.) Contempt and a sense of superiority 3.) Reaction to real or imagined grievances (see category #1). Usually only in the last category is it personal. No one who hasn't personally done something REALLY hateful, deserves to be hated.
Religion, ignorance, and jealousy can play a part in hatred. <br />
People who were brought up in a religious family learned certain beliefs. Their beliefs can cause them to hate on others simply because their religion told them what's right and wrong. <br />
Sometimes people hate what they don't understand or know anything about. They will ridicule and hate a person they don't understand.<br />
I know this one sounds very cliche, but it's defiantly a very good reason why people hate and tear others down. If someone feels insecure inside or someone has what they don't have, then they're going to hate on another person that is better looking or has what they don't have.
Neglect in education. Don't spend a lot of time grieving about it. it will take your power. If they are mean to you, they are mean to their own families. Meanness can't just stop on a dime.