Well the thing is a man should protect their woman but most guys wont or cant . The thing is most men dont know how to diffuse a situation and actually make things worse by using threats and trying to act tough . So I think it should go like this....
1) Step in and politely take your girl out of harms way
2) If he continues to approach instruct your girl (if there is one person with the problem ) to go to the car
3) Try to find a verbal or mental out ... Make fun of the situation ,try to downplay it
4) Be aware of his hands at all times and look for swinging posture... Allow him to be the first to swing and try to wrap him and show him he wont win
5) If all else fails drop him with extreme prejudice
