I feel the same way about someone hurting my dog, but what happens when an off-leash dog approaches and engages my leashed mastiff? Of comes all the way on to my somewhat isolated property and encounters an unleashed mastiff?
What's about to happen? Pretty much every time ... a choke-slam and impressive dominance display coming in T-3, 2, 1, .... No need to shoot the other dog, not gonna shoot my own over a dog fight.
Yup, EVERYONE is going to be unhappy.
In particular this pisses me off when they are on a woods trail I cut whose entrance crosses MY property.
Manage your dogs.