People who submit their opinions as facts. Facts can be backed up with unbiased evidence. Opinions are based on any particular person's feelings about a specific thing.
People who are jealous of those more successful.
People who dislike other people for being different.
Many haters feel they are justified due to either obnoxious or over the top behavior by the hated person.
1: Rappers are uneducated ebonics talking scrubs.
2: Ted has a smoking hot lady, tricked out ride, tight clothes, and a fat wad of doe; he's an ass... Fucking cock sucker... I'd like to beat him down. (This attitude is hating)
3: Tina just got a boob job. Why would she do that? Guys like natural better. What a slut... (Hater attitude)