Closest I've ever come to intentionally harming a dog was under similar circumstances. I was out in the middle of a field, working as a field hand on a tree farm. There was no place to seek shelter for nearly a mile (I had been dropped there by another employee and did not even have a vehicle). As I was busting my ass working, I heard some barking coming from somewhere behind me. When I figured out where it was coming from, I saw two German Shepherds in the distance that were approaching very quickly and sounding really pissed off. I stood there for a while thinking "these damn things better not be coming here".
When they were about 100 yards off, I could see very clear bad intent in their eyes, despite them both having tags and collars...and, boy, were they coming fast. I took a quick look at the tools I was left with and decided the hoe was the best way to strike with the most distance between me and the death hounds. I just prayed I could pull the hoe out of the first dog's skull in time to fight off the second. When they got about 15 feet away, they must have sensed what the hoe was about to be used for, because they came to a screeching halt and just paced back and forth, staring at me. It was like the end scene of The Good, the Bad and the Ugly.
Finally these damn animals got bored, or something, and trotted off into the distance.
I was scared out of my mind for a while there, thinking they would finally figure out they could flank me if they really wanted to. Not to mention, I really didn't want to have to kill a dog.
Drinking water now.