Your first mistake is coming to her defense....you should've just said, "Hey she's trash talking not me" and there's no way he's going to beat the crap out of a girl. If he did you simply grab anything you can get your hands on and crush his skull with it. Bar stool, Pitcher, beer glass, heel of your shoe etc.
I was with a date at a hockey game one time and there was a couple sat behind us. The girl jumped up and spilled her beer down the back of my date, who then turned round and threw her beer in her face. Me and other b/f looked at each other, looked at our beers, looked at each other again and just burst out laughing. It could've gone either way really but humour was the best avenue. Besides I didn't fancy fucking with him and he probably felt the same, and with the price of beer in the Capital Centre we weren't about to let it go to waste. As for the girls, we had the obligatory "BITCH - BITCH etc" then they started laughing when they saw us two rolling on the floor and the situation was difused.