I had the same issue not too long ago, I could either forfeit, or put up with it. I basically just chatted with the other players, and when the yahoo I was playing tried to be funny, I just commented on what a winner he was. Fortunately, the joker I met left too.
I did contact WGT, and they basically said there is not much they could do.
Possibly the screen shot idea would help WGT do something.
Most of the players are nice people, kind of like the real world.
Kind regards.