Pooches: Sidewalk Space and Dog Etiquette

Living in the city, you need to be prepared to deal with tight quarters. Even though we live in one of the more residential neighborhoods in the city, on our block alone there are probably 60 families and 19 dogs. This doesn't even count the random people and pooches passing through. Our block looks similar to this one:
Living so closely with other people, we're always aware of our sidewalk space and interactions. I always make sure the pooches are only on one part of the sidewalk so other people can pass by. I am aware that some people might be afraid of the dogs, so if they look fearful we'll step aside until they pass.At the same time, I expect other dog owners to be just as courteous. Our Pack just wrote a really good post about proper introductions; basically it's the idea that some dogs just don't like each other and they should never be forced to meet head-on. Our pooches also know walks are for training, and it's not a time to play. If we did let our dogs meet and play with other dogs all the time, it would condition them to get excited whenever they saw another dog. Plus, it would be dangerous to play on leash because the leashes could get tangled. For these reasons, I am very diligent about giving other people their space. We often cross the street to avoid head-on meetings, and I would hope other people would be as courteous.
Unfortunately, this isn't always the case. The other day I was walking the pooches and Miss M decided to go poo in the middle of the sidewalk. She had her back turned, and Mr. B was sitting next to her. From further down the block, a guy was being pulled down the street by a large "designer dog". As he approached I asked him to please wait and not approach my dog's turned back. Instead of listening to a small girl walking 2 dogs, that happen to be pitbulls, when she asked not to come near her dogs, he continued to let his dog pull him forward responding "It's ok, my dog's friendly" as his dog proceeded to smell Miss M's turned back. Of course, Miss M. made a correction as this dog snuck up on her, and Mr. B bounced around making scary noises. To this the man replied "You shouldn't be walking violent dogs" which made me so angry that I told him he should have "gotten an instruction manual when he designed his dog". I know what I said wasn't nice, but I was so angry that this man approached me when I asked him not to and he was insinuating my dogs aren't well-trained.
A similar situation happened a couple of days later, when I actually took my 2 dogs to step aside down the sidewalk as we were waiting to cross, and a man let his shepherd come lunging and snarling at our dogs, letting his dog go half-way down the sidewalk before going back his original way. I thought I was imagining how inappropriate it was until another woman walking her dog noted how that was completely unnecessary.I know my dogs and I don't like to put them in uncomfortable situations. Unfortunately, it seems not everyone who frequents our neighborhood is dog savvy. On one hand, I want our dogs to be good breed ambassadors showing people how family-friendly pitbulls can be. On the other hand, this makes random people want to approach us and I really don't want to deal with the excitement, leash pulling, and reverse conditioning; it's almost like I wish those people were afraid of us so they would just leave us alone.
Does this ever happen to other people? If there isn't enough time to explain why I don't want my dogs to be introduced on walks, how else can I deal with these types of people?