I personally like the "stop the game & tell everyone else who's fault it is" approach. Getting into physical disputes solve nothing really and as many others have said, leaves you open to assault charges & potentially a world of pain if the other guy is tougher than you, or his mates decide to get in on the act. Telling his mates that it's HIS fault that they can't play any more however tends to put them on your side, and peer pressure is a wonderful tool especially if (as I feel may have been the case here to a degree) they are misbehaving to show off.