You are certainly right in that it was an appropriate place for the dog to be. And many dogs are very protective on their own turf, even if they're normally quiet and loving. BUT - that doesn't matter. When the cops enter in a situation like this, if a dog - any dog - acts in a threatening way, their only option is to prevent it from attacking...and they probably have 2 to 3 seconds to do so. If you were the cop, you wouldn't be taking a chance on having it chew up your leg.