Originally Posted by mr dave

The difference being it was in Vancouver, a city known for having a very substantial hard drug problem. Some guy beating on a city bus (on a street that has the dubious reputation of being one of the worse in Canada) in the middle of the summer because others didn't act like a cab towards him is a worthy concern. Yes, the police could have waited for the next time he did something stupid, but that next stupid thing might have been to assault someone's mother. Your mother.

Then what?

Then you've got the family and neighborhood (and the rest of the internet) all screaming about where was the police to stop this person before they did something so horrible. Then they find out that person got left to wander after a previous public display of physical violence and complete lack of self control? It's not like they didn't try everything else first. The article specifies they'd chased the guy into an alley, and he still refused to cooperate. At that point, where they don't know just who or what is waiting in the alley with him and his refusal to cooperate or calm down the situation becomes risky enough to merit using the dog to take down the suspect in my eyes.