Furry piranhas needs education

This afternoon we walked to the park nearby for the dogs to run off some steam. We have not taken Pita to the fields yet, since she simply cannot manage such long walks just yet. She is still too small. There was a couple sitting on a blanket on the grass, and we let the dogs off the leashes. Barak is very aloof and never approaches strangers, while the pup of course (also being a Pit bull) ran straight up to them, and they were of course enchanted. Right now she does not scare anybody, but in time she will have to learn to stay with us and not run up to unknown people. Anyway, they started to play with her, and of course she used her teeth. They just kept on triggering her. At that point I started to intervene, upon the woman explained that she didn't mind. Then I explained to her that this little pup is actually not allowed to use her teeth on humans, simply due to the fact that although it might be cute now when she is 9 weeks old, it will not be that cute when she is a 9 months old muscled Pit bull. Then I added that she is actually a Pit bull and not a poodle, and that she has to learn good behaviour. They understood and looked a bit embarrassed. This attitude is precisely what makes ignorant people lose control over their powerful dogs, and it really ticks me off.