Why is Dionysus in Percy Jackson so much of a jerk?

I have been reading Percy Jackson books for the past 2 years, and I want to ask this. Whats Dionysus' deal?!? He's always being so irritating, it's not even funny. And to be even more irritating, he purposely says Percy and Annabeth's names wrong.I don't care what you say, but he's a total jerk!