purposefully sprays beer in your face, they have already assaulted you (and actually battered you from a legal perspective .... "mmm, beer batter"). I can't even imagine somebody getting in legal trouble for at the very least pushing somebody away that was spraying them with beer. I think it unlikely you'd get in trouble for punching him, honestly ... possibly getting kicked out of the game, but that would be a pretty small price to pay for my dignity. To each their own, I guess.