I guess I just never had an opportunity your friend had to get in a scrape with a gang banger. Parties, bar, clubs, girl's houses, on the street or at home, I just never had a chance to meet up with a banger in such a manner that would lead to a fight other than PAL summer camp we all used to go to. The neighborhood where I grew up, everybody just stayed out of the fray. As long as you weren't a snitch or in another gang, you just bided your time till you could move on out of the place.
I'd tell your friend to move. Cause if the guy loses face then his set loses face. So the guy your friend "beat the crap out of" might be a mariposa, but his crew is going to look like a bunch of pussies to the rest of the animals. They don't like that and that's when things get a little dicey. I don't mind fighting. It's just that these animals don't mind killing or going to prison. They think of it as "continuing education" or a resume enhancer.
I always thought the tough little gang banger didn't want anyone to know one guy in his 40’s had beat the crap out of him, so he told everyone it was a group that did it.
Then again my buddy didn't give the guy a chance to turn around he nailed him from behind and didn't stop.
Gang bangers moved from where they were living about a year later. Hazmat team had to come in and do a cleanup, had a meth lab in one of the trailers on the property.