I love the way the non-rule-compliers somehow make the problem into YOU with your "non-friendly" dogs (smack forehead).
I had this problem for years - Cattle Dogs are by nature, a protective sort of beast - and a loose dog that was bounding towards us was going to get hurt if it came too close. Fortunately, a Cattle Dog in full "protective mode", standing silently but poised for action, with hackles raised 6", is fearsome-looking enough that most people quickly called their errant dog back after I mentioned that my dog is NOT dog-friendly.
But now I have two snack-sized fluffballs who couldn't garner a half-ounce of ferocity between the two of them. We haven't camped since we had to put the Cattle Dog down - but I'm going to have to carry some sort of defensive stick or spray, I guess.....