I'm new here, a new doberman owner, and my last dog was a GSD. I'm also a cop who has had to shoot dogs (in my cases, they were loose and had either attacked or were trying to attack people) and also, when possible, managed to avoid it. I understand both sides of the issue, and I can tell you from my own experience having to do it is an emotional experience especially when it's not the dog's "fault".
Pepper spray sometimes works, but how many of us would expect our dogs to fight through pepper spray to protect us from an intruder? Taser is extremely difficult because both barbs have to hit, they are designed to spread, and dogs are difficult, small, fast moving targets when you know you have a barb spread to deal with. There are cases in which both these options have been successful, and cases in which both these options have failed and officers have received career ending injuries.
I also feel it's disingenuous to expect someone to know whether your dog will bite or not (many owners don't even know what their dog will do when confronting an intruder), or to minimize the power of these dogs. I have seen devastating, life threatening, permanently disabling, and fatal injuries from "family pets".
I have always operated on the belief that it is my duty to do everything possible to avoid shooting a dog on his own property when I am moving through on a suspect chase or track. I have managed to accomplish that despite some downright frightening encounters. I have been fortunate that the initial posturing of the dogs has given me the window of opportunity to find a way out of the situation.
That said, if I found myself facing a charging dog with no way out I would shoot. I would lose sleep over it, I would be emotional about it, but I would do it. Likewise, if officers went through my yard and encountered my GSD or doberman, I would be extremely upset and heartbroken but I would also understand because I've been there and I know how fast things can happen.