Good for you! But one day....
It isn't implied. If they feel threatened by man or beast they are trained and allowed to take action according to the law.
"one day" has already came. I had my nose nearly ripped off my face by a dog when I was a kid. On another occasion, I was biking on a public trail and got chased by a dog that seemed to want to tear me a new orifice. I had a 9mm in my frame pack, but managed to refrain from killing the beast. And I still don't feel the need to kill any dog that approaches. The point is, there were two cops. If one of them got bit, the other one could have shot the dog. Or they could have hit it with pepper spray or a taser before that happened, or whacked it with a billy club. Getting bit by a dog isn't the end of the world, and IMHO doesn't justify discharging a weapon in a suburban neighborhood.