The verb form of the word hate has recently undergone a minor innovation in usage. Occasionally, it is made to take the preposition on, as in "Why are you hating on me?"
The definition of the word appears to be slightly different in this usage. Instead of hating an object internally as an emotional state of sorts as would be the case in the usage "I hate sunlight," a person hating on an object is in some way externally venting some sort of hatred. That is, "X hates on Y" means that X is doing something that makes Y feel hated, such as insulting Y's single puny bottom thing which pales in comparison to the manly pair on which X rests. Or, y'know, whatever it is that letters of the alphabet are sensitive about.
This usage tends to be associated with Ebonics, although it need not necessarily be.
This has been your linguistic newsflash for the day. We now return you to your regularly scheduled noding.