The bottom line is that if your dog gets off leash and runs “at large,” (which is illegal), then you are not controlling it. I feel bad that Pitties and Rottweilers end up with these bad reputations, but as someone else pointed out, many people get these dogs for their reputations, thus perpetuating the negative stereotype.
Always keep your dog on leash, and if you come across other people while walking him, make him sit or move across the street to make sure they don’t get a bad impression of your dog. It can become a legal liability. For whatever reason, people don’t seem to care that there are Chihuahuas that are, pound for pound, as aggressive as a fighting pit bull. Because they only weigh 5 pounds, it’s seen as cute.
You can’t assume that any random person is going to like your dog, however harmless it may be. For the sake of your dog, be as exemplary of a pitbull owner as you can be. You will change minds in the process.