They are not bred for "relentless aggression" and the notion you could even breed for such behavioral characteristics in just a hundred years is laughable at best. Please read the source material I posted for fuck sake. Every time this comes up a bunch of people show their ignorance and bigotry.

In fact pitbulls were bred specifically against human aggression because of their use in fighting. If a pitbull attacked a human they were instantly put down for generations.