I'm a huge supporter of 21+ drinking laws. You gain a little perspective by the time you hit 21 IMO. Then again, I come from a country where that was the law...didn't stop me from obtaining a fake ID though. Did stop me from acting like a tool (in fear of losing my fake ID) AND it stopped me from drinking like an idiot cuz I didn't want to seem like the dickhead in the bar/club.
I saw way less fights in the states, inside and outside the clubs/bars. Not saying they didn't happen, but not near the main drinking precincts. Then again we also have 2am licenses in CA, so everyone's either booted out of the bars/clubs at 2am OR the alcohol is stopped being served then with a lock-in to full effect. Made clubbing interesting in SF, cuz San Jose didn't have any lock-in clubs. Lock-in clubs made lots of money selling "energy drinks" and "water", let me tell you...I wonder what else was sold by the bartenders? Hmmm??? But this wasn't why there weren't many fights...
To put it in perspective for folks, I was quite used to coming out of clubs at 2am when they closed in San Jose to see 15 cop cars and 50 police officers on the street (our main drinking precinct was along a main street). They were simply there, in full riot gear, to keep the peace and "escort" those who were too messed up into awaiting paddy wagons. They'd take note of bars who were sending out the really messed up punters and these bars would get on the spot fines for serving drinks to people so messed up. My girlfriend at the time worked as a bartender and her bar had it happen once or twice. It was the cops way of enforcing responsible drink serving.
What this ensured was people who really wanted to party made the 45 minute trek to San Francisco, by train if you were smart, to party at the late night "lock in" clubs. Obviously with the help of narcotics, you'd stay til daylight and walk the wharf precint til you were ready to make the train journey back to San Jose. This made San Jose a really dull clubbing/party city, but that's what the people in San Jose wanted, for better or worse.
I know this from people I know...I stayed at home always eating cookies and drinking milk whilst reading great literary classics.