Warning, fairly irrational rant against OP and pitbulls owners ahead.
He was in the wrong if he wasn't using a leash, and it wasn't his right to tell you such a thing, but I sympathize with the sentiment: pitbulls are killing machines and I cannot help but feeling that whoever owns them is just overcompensating for something else, no matter however irrational this thought is. Among all the dogs you could have chosen from, why a fucking pitbull? What difference is there between a pitbull and some other random dog, with the exception of the former being much more aggressive and dangerous that the majorities of the other races? You never hear stories of chihuahua killings children, and even though the pitbull who have done so may have not be raised well, the fact remains that this race and few others are the only ones that are reported in similar stories.
Sorry OP, I know that my rant was uncalled for and that it is way off topic, but this is a pet peeve of mine, I really don't understand people who willingly decide to raise such potentially dangerous pets. It's a frightening thought, especially because I fear that many people don't recognize their being a danger.