Don't go to parties with violent people
Your friend needs to avoid three things:
1) stupid people
2) stupid places
3) stupid things
If you have a buddy who tends to get obnoxious when he drinks, then maybe he shouldn't be your buddy.
If your favorite bar is "a little rough," then maybe you should go look for one with hanging ferns (or better yet, do your drinking at home).
And finally, avoid doing stupid things. Going to a Harley bar and yelling "Harley's suck" is an example of things to avoid.
As for your friend, he never should have exchanged words with his assailants. When you are carrying, you need to be casper milquetoast with no ego. He should have been apologetic, put up his hands, and backed on out of their pronto.