Now, before everyone starts getting butt hurt and saying it doesn't work, this only works right after you've become a "bad sport". So if you've been a bad sport, it's not gonna work.

Basically, when you become a bad sport it is saved as local memory until it syncs with the server.

So, when you get the dunce cap , it tells you the time you have to serve or whatever. Wait like 2 seconds and then dashboard (or PS3 home if you're on PS3) and then start up single player, press start and join a game.

If it worked like it's worked for me, you wont have the dunce cap anymore and you wont be a bad sport either. Hope this helps/works for you dick heads and have fun blowing cars up!

Credits: Trill from HackForums, if I hadn't seen his post I wouldn't have figured this out for myself.