I know what you mean. But you have to man up. It's a cruel world, bud, and people do this all the time, just to make you mad or depressed. Don't just sit there. And if you are too lazy to contact a GM, flame him so he's pissed off, too.
And to solve a ridiculous problem like this, just do /opt chat 0 and it removes the chat.
But you have to remember, people in this generation aren't nice anymore, just lighten up, ignore them, and move on with your life.
Or just simply stop going on the internet.