From what I've seen, most pit bulls are well socialized friendly animals.
They CAN be dangerous, and can certainly cause more damage than the football size dogs that have been the only ones to get aggressive with me.
I will stress that a pit(or any dog for that matter) should always be attended or secured away from unfamiliar people and animals.
Dogs are social animals, they are capable of taking clues from their humans on what to do. Friendly greetings? They look forwards to pets and scratches, playtime. Attack their people? That'll lead to the dog defending their fellow pack members.
My grandfather's dogs, boston terriors, attacked a person in at least one case - he was trespassing in gramp's backyard while trying to evade police and kicked a mostly grown puppy - never saw the others. Ended up with having two females(one the mother) holding onto his legs and a male with his mouth around the guy's throat that growled* whenever the guy tried to move or talk. Got to lay there quite a while as animal control was busy on the other side of the county, and the cops weren't willing to enter the yard(Grandpa might have more dogs), shoot at the dogs - the goblin wasn't hurt, and the dogs small enough that to try to shoot them would be to shoot the goblin. Grandpa finally got home, entered the yard with the police to shoo the dogs off so the police could arrest the crook.
Was a bit hilareous as the goblin tried to sue gramps for having vicious dogs - despite the fact that they never broke the skin.
*I imagine that it must have been an interesting feeling