This is not really about pit bulls or poodles or Chihuahuas. It is about cops, their lack of tactics, and their perception of the need to charge into every situation without considering alternatives to bull-in-a-china-shop behavior. There is nothing that indicated the cop could not have retreated back into his vehicle and used the PA to call the dog's owner to restrain the animal, or the radio to request Animal Control to restrain the dog.
Someone was where their restraining order said they were not supposed to be. There is nothing to indicate they were committing any violence or mayhem at the moment. But the cop felt he needed to bust in right then, right there, and do "something" - and got himself needlessly bitten by a dog that was, at worst, territorial and at best responding correctly to behavior threatening to "his" pack.