Then you were around people who can't control their dog. Pit bulls ( and I use that as a general term for the uninformed, because there is no such thing as a pit bull. There are American pit bull terriers, American staffordshire terriers, staffordshire bull terriers, and American bullies) are naturally dog aggressive. It's genetic. Not all of them are, but it's common. Just like a German shep, or rottie are known to be human aggressive. They are a protective breed.
As for a pit. They should never be human aggressive. That is a trait highly frowned apon in the breed. Yes they may protect their family, but most pits know no strangers. If you were bitten by one then my guess is the dog was stressed and you happened to make it or the situation made it feel threatened enough to act out.
As for the attack on your dog, that a pit doing what they were bred for for hundreds of years. It sucks I know. That's like being upset with a border collie herding sheep. It's what they were bred to do.
I'm so tired of people and the media making this breed out to be monsters. The people who own one has to be able to deal with all the good and bad traits of the breed. That means controlling a DA dog.
To the OP. great story. Sorry for the rant. I just can't stand the bad rep.