There's much more sadness in life

Suddenly, I felt my whole world is falling apart for some stupid people, not stupid, childish and ignorent people. I felt stupid & dumb feeling angry for the people who doesn't care. Just now my best friend (guy) say one thing that I think, maybe, I would not able to apologize him. I know he's angry with me. But I don't know the reason why. When I'm tagging the pictures of my friends and buddies, I tagged him a sports maniac. He comment : LOL! I want to tag you as a bitch, why don't you tag it yourself? Bitch, he called me a bitch. I'm quiet furious with it so I reply, o0o back off. Then he replied, "haha..cho sial lo". I do not know what to say. I mean, what do I do to be deserve being call a bitch????