People who improperly breed pitts should be shot too.
Pitts were originaly bred to fight other dogs. They were not designed for protecting people, they were intentionly bred to have the least hesitancy to attack. I find it cruel and am against dog fighting but several dogs were bred in the 18-19 century for dog fighting, or mousing (where they bet to see who could kill the most rodents in a pen in the fastest time, terriers were bred for this.) Pits are a combination of terriers and muscular fighters, so they inherently have the attacking instinct of the terrier and the power of something larger.
However modern dog breeding focuses on looks (that were originaly just a coincidental thing) and not ability to perform the tasks the breed was designed for. The AKC for example is more concerned with the perfection of the animal's colors, coat and walk than its intellect or ability to perform the tasks. So in fact the good temperment of a pit bull is due to bad breeding, not the reverse.
Fighting dogs training is cruel and I hate to even mention it, but it includes record keeping of which dogs cower or ever stop fighting due to injury etc. A dog that is foolish and willing to die and continue fighting even after losing a leg is considered superior breeding stock to an animal that realises it has lost and submits or ever hesitates and thinks before attacking. So they are by design supposed to have the least thought between feeling the desire to bite and biting. To have large powerful jaws, and to have a high pain tolerance. These combined features mean that killing such a dog is the only way to effectively stop the damage they are inflicting immediately.
Now combine this with a terrier which was originaly by design supposed to desire to kill small rodents as fast as possible and you have a poor family pet.
It is because most dogs are bred for coloration and not purpose anymore that has allowed enough dilution of thier gene pool to even make such a bad breed a house pet. When people bred dogs for purpose a brand new pit bull puppy even with the best upbringing would have grown into a dangerous dog to have around children or other animals. Some are still this way, others are diluted enough to do better.
A loving enviroment and proper ubringing and training can make them less of a liability, but it does not change what they physicly are and the short circuit their brains make in some situations by design.