@Duke:
True, except for the fact that all dogs have the potential to bite. We had business in the store for training which includes polite greetings with strangers under my supervision. My supervision was inhibited as I was trying to pay the bill. We could have been long gone if people didn't interrupt and invade my dogs space. The person in line was thoughtful to maintain good distance for me. Duke had about 4 feet of leash or the potential to be maybe 3 feet from me. I just got frustrated - and I think Duke sensed it too. My efforts to reinforce polite greetings got a bit stomped on - but we'll keep working on it.
Opinion Alert
True, every dog has the potential to bite, but some are far more likely to do it than others. And when you know you have one that is more apt to bite, I feel you have to take extra ordinary precautions. Maybe, put the dog in the car for the little time it would take to shop/pay the bill, or being sure to have cash/cards ready before you get up there, etc., or shop another day.
I understand that you were there for training. But once you started shopping/paying, etc you weren't in control or a controlled setting. Unfortunately, all it takes is one second to have a lawsuit, an injured child,{or adult} and a euthanized dog {or a dog fight. My vet has a few horror stories about PetSmart and PetCo emergency injuries he's had to deal with}. Regardless of how we all feel – and we are ALL in agreement about people feeling so free to grab at any dog -- when we have a dog that we know is likely to bite, we just can't let ourselves be distracted in a public setting, IMO.
If it were me, I don't think I'd START friendly greeting training in a store, where you don't know who you'll encounter or what other dogs may be there to excite yours. I wouldn't take a dog there {for shopping purposes; I understand you started out at a class} until the training had been going on successfully for a while. Again, though, that's me.
I do have empathy for the frustration you felt. I think most of us can relate, esp. those w/dogs that aren't crazy about strangers.