The genetics for dog aggression were present in pit bulls before they became popular. Their numbers in the overall population were not that high to have much influence on bite statistics. Don't be fooled into thinking aggression was put into pit bulls recently by those you refer to as jerkoffs.
What I am talking about is the lack of evaluation for these genetics by those breeding for pets, breeding for a dog that looks tough, and those breeding to make money off of a popular breed. It is no different than those breeding pointing dogs and not evaluating for the genetics of pointing; they have no idea about how the pups they are producing will react to birds. But misguided or incomplete pointing genetics are not a public health concern like misguided or poorly balanced dog aggression genetics.