[officialtony]

I have heard more horror stories like this than I care to remember.
I have turned down those kinds of " fun " games before since I have heard the horror stories. It is NEVER for fun. There will always be at least one stud in the group who will be out to flex his baseball muscles and this will lead to egos getting puffed up, etc. I just don't do these games and I would encourage you and others to avoid them like the plague.
Just politley inform the party asking you to work the game, that you have a previous commitment and let it go at that.
Hopefully a lesson well learned.