I agree with Petrefax. Its difficult to know what you'd do till the situation occured, but Id like to think I would do something
As he says, theres always one whos dominant, so you find him, and take him out as quickly as possible (I find the nose, the testicles, or a cupped hand slapped over the ear most effective ). Once youve done that youve got the upper hand, and its much easier to sort out anyone else.
People who prey on the weaker members of society should be ritually beaten, and preferably crippled, so as to never be able to cause any more damage.
If any political party takes this up in their manifesto, they bwould blatantly get into power next term, and lets face it, one term would probably be enough, as a good kicking only takes about an hour on average