From what I understand, the official name of a "Pitt Bull" is a Bull Terrier. Originally , these dogs were bred to help herd cows...not aggressive, but territorial. They were supposed to be big and strong enough to grab a bull by his most sensitive part and bring him to his knees to prevent stampedes. They did this by locking onto the bull's nose and not letting go.
What ended up happening, when nasty types who breed fighting animals found out that Bull Terriers basically lock their jaw and are almost impossible to escape, they took the over-aggressive ones that the herders didn't want and threw them in the fighting pit.
As more effective ways of herding/controlling cows were discovered, the Bull Terrier lost it's draw as a herding dog. That meant that the majority of those who bred these dogs, bred them for the fighting arena. Over the years, the reputation as an aggressive, hateful dog became a stigma that led lawmakers to pass harsh laws on their breeding. Granted, if there are fight dogs in a family line, there is a good chance the dog might be aggressive. But to say that ONLY aggressive bloodlines are left is stupid.
As for the breeders, most reputable breeders of purebred show dogs will simply sterilize an animal that doesn't reach Kennel standard, and place them in a loving home. Only those who have no respect for life, and only see the dog as a commodity to be exploited will kill the puppies. Most of these breeders are probably doing something that will get the ASPCA on their case anyway.
I also know that there are programs out there to place retired racing dogs in good homes.
Yes, I admit, I used to watch WAY too much Animal Planet.
You say "Witch" like it's a bad thing!