I love dogs, too. But the only time I've ever fired a gun under duress (my 6904, actually), was when my dog was attacked by a huge Shepherd and a Rottweiler in the woods. A warning shot ended the scuffle... luckily I didn't have to kill the dogs. But I would have, to protect my dog.

I think the guy did the right thing. That dog was a clear danger. Probably more the fault of the owner, though, than the dog itself.