Although I share your sentiments (precisely share them). You missed my point entirely. LEGALLY anyone can shoot your dog, and the consequences are minimal. If you retaliate and return fire, YOU are punished. Hence, cowards and sadists know they can hurt you by killing a loved pet.
If laws are made to protect pets, then are we giving animals the same level of protection as humans. So, if you shoot a nuisance rat, squirrel, pidgeon, snake ... will you serve time in jail. How do we differentiate extending legal protection to pets, without crippling varmit control?
Personally, if you shoot my pet; you may have just as well shot my wife or kids. Just like you, my revenge will be cold, hard and permanent at a time of my chosing.
If your dog is large enough, loose, and threatens me or any member of my family, your dog is going down hard. If you want to continue the stupidity and take murderous vengeance on someone who acted to protect themselves from your mangy cur, then be prepared to rot in jail (or fry, if you live in Texas or Florida).
I love my own dogs. But I never forget they are animals--not humans. And I also remember they are none-too-bright and must be well trained to curb the instinct to attack people outside the "pack." Even then they run the risk going to the Big Sleep early if they attack or threaten to attack innocent people.