I am a little apprehensive what to make of this. I think there is a tendency to be slightly biased against the cops here, as the video footage suggests a poor helpless man. The video footage steps in far too late, perhaps through careful editing to remove any damning footage showing the guy in a negative light. Was he drunk, I suspect he was since bouncers called for assistance so I doubt he was some innocent little angel standing there minding his own business.
Personally if your out for a confrontation then chances are you will get one squarely between the eyes most likely, with either other people or the police. If your'e going to behave like an animal don't be surprised if you end getting treated as such. I personally have had no problems with police not because I love them, far from it, its because I give them a wide berth to try to avoid these sorts of situations.
Problem with this sort of video footage and Youtube ever since the infamous Rodney King police battering everybody wants their slice of the fame by trying to make prime time news with the footage they have shot. Obviously the footage would not be quite so dramatic if it was shown to be slightly more two sided. Call me a cynic but the old adage "belive none of what you hear, and half of what you see" is a good general rule of thumb that applies in many situations.
This is not that extreme when compared to brutality dished out by lesser developed nations police forces Pakistans Karachi cops spring to mind, where you might be beaten simply because they dislike the way you are eyballing them.