As the saying goes, the problem usually isn't the dogs it's the owner(s). It takes a lot of work to properly train a dog, and MANY owners don't take the time to do that. Unfortunately pitbulls are the dog of choice for dog fighting and get discarded therefore many in shelters or on the street have been bred to fight.
I've had pits my whole life, been working with them for years. Had a 110 pound pit/lab mix who passed away from cancer last year, and we still have a 85 pound pit/rot mix and a 60 pound pit terrier.
We've fostered numerous pits with rough backgrounds. Some dog friendly, others need to be the only dogs in the home. Some can't be saved because of how they've been trained and how aggressive they are but in many cases they're big babies and terrific family dogs. We have ours and our fosters around kids all of the time with no issue.