Back in the days when I was assistant managing the sculpture garden, I worked with the cops in regard to many a noise complaint. See, "Jazz in the Park" was actually "Jazz in the Park Next to the Retirement Community Condos," so we got a noise complaint many a Sunday afternoon. Why Jazz music floating on the breeze across the river and to their condos was such a bother, I'll never know.
I don't know how it works elsewhere, but we had a city issued noise permit which allowed us to create noise up to a certain point - it had something to do with how loud we allowed the bands to set their amps. I took a look at the permit once and it was all about accordance with zoning by-laws and such. We were always compliant with the level allowed, but if a complaint was made the cops would come by to check. Normally a happy cop (what a nice call to get: "we need you to go take a stroll in the park on this lovely day, check out the jazz music, make sure they don't have their amps set above 8, etc.) would come buy, my staff would be all paniced at the sight of a police officer and send him my way, the cop would either want to go up and check the amps, or would just have a polite conversation with me about the complaint, and how as far as he could tell we were within the limits... one time one cop did turn the amps down, but thankfully it was during a break in the set.
So, anyway, I agree with those who post that the cop shouldn't have made the issue the band's problem. It's not the band's problem - clubs have managers and staff that are clearly in the line of command to deal with complaints. I can't walk into a club without someone stopping me to pay cover, show ID, etc, so I also wonder where the staff were at this club. When I'm at a bar and the cops show up, usually the staff is right on talking to them the moment they walk in the door. Did this guy just charge the stage from the street? It's pretty hard to imagine that being the case. Even for the most roided up guy. He's a total idiot for taking on the situation on his own if he really felt it had escalated to a level where he needed to approach the stage, as he aparently did, but someone must have approach him/met him at the door and said "Hi, I'm the manager/security guy/owner, is there a problem?" And what happend after that? Every club I've been in, when the cops show up, all eyes are on them - including the staff - the moment they cross the threshold. Then again, locally, I've never seen a cop enter this sort of situation alone - the local cops patrole bars in pairs.
We have some horrifically crooked cops locally too, so I do sort of impose the idea of this guy being full of uncontrolable 'roid rage onto the situation, but the way it's being presented sounds way too black and white.