I'm kind of getting tired of the attitude I see in some (not all, of course) nippy herding breed owners that their "well-mannered" dogs have a right to correct dogs that are doing as little as behaving too bouncily in their vicinity. Yes, my dog has a very, er, straightforward approach to other dogs, and it intimidates or annoys them and gets him into trouble. He is a rude dog. However, your dog that jumps straight to biting any larger, sniffier dog that comes too close at all? Also not manifesting super polite dog behavior.
And I really wish there were a way to communicate to these people without being misinterpreted that, while my dog looks and acts goofy initially and loves other dogs, he doesn't back down easily at all. Now, I work very, very hard to keep him out of other dogs' ways when we're in multi-dog situations unless the dog is VERY obviously accepting and tolerant, and I am virtually always successful.... however, if for some reason something were to happen and he got too close to their nippy dog, that dog would not be effective in "teaching him manners, hahahaha!" as they seem inclined to think. One of two things would happen:
1) The bite would not be enough to make him feel threatened, and he would keep doing what he was doing.
2) The bite would be enough to make him feel threatened, and he would fight back.
And he is bigger and often physically harder than many nippy herding breed dogs. So there is a strong chance that, while it would be bad for my dog, it could be worse for yours.
My dog being rude in his approaches and not knowing when to take a hint isn't cute or funny, but neither is your dog overreacting about it and trying to throw a first punch. It's just another source of trouble.
(Note, I do of course think there is a time when it's appropriate for dog-dog physical corrections to happen. I'm just stymied by some people's desire to minimize their dog's tendency to "overcorrect" other dogs' essentially non-threatening behavior and potentially escalate the situation.)