You were totally right to have done that.
In my old town, one of our council members had a dog, Riley -- a black lab or something. The town has a strict rule about leashing your dog, and this council member would give anyone he saw with an unleashed dog a hard time. He NEVER used a leash for Riley. I wish someone had reported him.
I love pits, but if you ever get an uneasy feeling around them -- or any dog for that matter -- its best to just leave. Because even if they aren't planning on doing anything, they sense that the person is stressed, so they'll get stressed -- and that can only lead to bad things. Yesterday at the dog park there were no dogs on the little dog side, and the dogs on the big dog side were all small-ish, so we took Tucker over there. When 2 pits showed up, I started getting uncomfortable. And I'm a pit-lover. One of them was very very sweet, the other seemed more...anxious or something. When I started getting nervous, we left, not because I thought the dog would just lash out, but I didn't feel comfortable. Better to be safe than sorry.