Pit bulls were NEVER bred to be people aggressive, for hundreds of years these dogs have been bred to be animal aggressive - where they think they originated from - it was large game like lions, boar, bears, etc...Then bulls back in Europe for butchers - they would hold onto the bulls noses like a lion does and hold and partially sufficate the animal so the butcher could deal with it. Then they became bait dogs - bulls, boars, rats, etc the dogs were put into competition against animals for the pure sport of blood and proving who had a tougher stronger dog. Then it went on to being easier to hide the blood sports by selectively breeding the bull dogs to be dog aggressive and pitting them against one another - it was a chain of crueling training these dogs and selectively breeding the more dog aggressive dogs to get the traits. However - for hundred of years any PEOPLE aggressive bull dog was typically put down because while they wanted them to be dog/animal aggressive they were still family pets - these dogs back in the day meant alot of these people - even though they thought it was okay to let them tear themselves apart. They didn't want a dog that may bite them or their children in their home or yard...
Pits until recent years (past few decades) were never bred to be people aggressive - they don't make good guard dogs AT ALL it isn't in their nature, and this is why when someone wants the 'tough bad boy looking pit bull' to be their 'guard dog' it takes ALOT of CRUEL training to get them people mean, and this is by aggitation training, blood training, and bite reinforcement from a YOUNG age...Then they breed these dogs to start the aggression in the genes and you get dogs that are people aggressive...
Around here the dogs that have bitten the most people according to a lady who works in the hospital here - border collies and dalmation purebred/mixes are the most common biters and its due to poor breeding.
A pit bull SHOULD make a great family pet - if not inbred or poorly bred (with people aggressive heritage)...However MANY pit bulls if not exposed and trained well at a young age have a good chance of being animal and dog aggressive. That IS in their genes - but doesn't mean its going to over rule the way they are nurtured and trained. I've seen rescued fighters become great family pets with other dogs and cats etc...But they are the exception to the rule, in general a rescued fighter is not a dog I would feel comfortable letting around other dogs - but with people? Most rescued fighters are people loving goofy fools.
A pit is like a shepherd or a collie or a hound, they were bred for a purpose - and even if the past 3 generations had nothing to do with that purpose - say a collie is a herder - you may get a border collie who bites kids ankles/legs trying to herd them and just being anxious because it doesn't have something do to do to burn off energy and that inate trait thats in its blood has come out - and it trys to find a way to do what it feels it should be doing...You can circumvent the biting/want to herd by walking and exercising - agility, etc... A hunting breed, just playing games/exercises that uses their sight or noses (depending on kind of hunting dog) to get them active and using their instincts.
A pit isn't right for every person or every home - just like a coolie or a beagle or a yippie chihuahua isn't right for every home.