I was chatting to a hockey umpire in Calgary a few years back. He told me that all umpires allow a certain amount of fighting as it releives a bit of tension and frustration which in turn may stop someone getting seriously injured.
The moment a stick is raised or the gloves come off they have to step in and stop it. He said a guy had been killed a few months earlier by a stick that was swung at him deliberatly. In the case of this video there were so many fighting all control of the game was lost.
I can't believe the crowd was booing,they got a lot more than they paid for. I would have paid good money to be in the crowd