Pits were not originally bred to fight bulls. That was a secondary use. There use as fighting dogs was based on their use as hunting dogs. Your lack of knowledge on the matter and persistence is remarkable. Really want to call my parenting of my children into this? You are something else.
BTW, what is your personal experience with this breed?
They have a FAR greater aggressive history over most other breeds, they also do more damage. Your woeful lack of responsibility is dangerous to your kids health. YOU brought them into it, not me.
http://en.wikipedia.org/wiki/Fatal_dog_attacks_in_the_United_States#Fatalities_reported_in_2014