A person who would kill a law enforcement K9 would kill a law enforcement human given the opportunity. And should be treated accordingly. I have never been forced to take a human life, but could if forced (trained to do so), and to a man, everyone I know who has been, and I know several, would shoot a person who shot their dog, with no hesitation.
Criminals decide what their life is worth when they decide to commit criminal acts. Law abiding citizens are often forced to act on that decision.