Not all dogs require training. Some are simply good natured. Some require good training but bad owners don't give it to them.
What about German sheppards? Or boxers? or any of the many other aggressive breeds? Do you feel the same way about all of them?
I've wanted a german sheppard in the past but decided it wasn't for me as they required more attention and training than i could provide at the time, might revisit this down the road.
I'm cautious around large dogs / guard dogs in general but pitbulls are on another level