Plain and simple. You can go into a bar and talk about someone momma, but if they punch you, it's still assault. The police seem to have witnesses that stated Zimmerman was returning to his vehicle when Martin approached him and started beating him. If that is the case, he has the lawful right to defend himself if he was being endangered. Whether he was under age or eating skittles isn't relevant, if he threw the first blow, it's self defense.