Your post proves my point. The first one was off duty, that's no different than any FReeper walking down the street and defending himself from an attacking dog. I've heard FReepers say many times they'd do just that if attacked. It's one of our rights is it not?
Three of the others say the officer was being attacked and only one, the Miami story, should maybe be considered an officer error, and that only because the officer did enter a secured yard where he could have possibly avoided the dog in doing his work.
But back to you proving my point... in a country of over 200 million people, how many cops have made home visits this month, some friendly some not, where a dog was present. Just statistically? a hundred thousand? Two hundred thousand? Guessing here. Six ended up where a dog was killed and most look like good self defense. I wouldn't call .003% ~common~, would you?
And every day how many mailmen, parcel delivery men, garbage men, and utility readers visit those same houses with those same dogs? You don't read of those people killing dogs in the same numbers that policemen do. They manage to carry out their visits by such means such as knocking on the door, asking that the dog be restrained, use of pepper spray, etc. Only the policemen seem to first use deadly force as a be-all and end-all solution.