Saw a really interesting documentary on canines. They included a segment on Soviet efforts to breed tame silver foxes. From a captive population of approximately one thousand foxes they began breeding. The first captive generation they had about 1% that showed indifference, neither fear nor aggression, toward humans. They bred these with each other and in two generations had tame silver foxes. The really curious thing was that other physical traits in the silver foxes changed as well (although not specifically bred for these traits, they were just concentrating on the temperament), and the resulting foxes looked more 'dog-like'.
Anyone that thinks aggression is not a genetic predisposition in breeds is simply uninformed.
Or willfully ignorant. <- My vote
Pit bull apologists are always blaming factors other than the dog. “It was provoked.” is a favorite, followed by “It was the owner’s fault for making the dog vicious.” Well it always is the owner’s fault legally, but that’s not what they mean. And as far as provoked, your mere presence where the dog can see you is often all the “provocation” these dangerous animals need. I wouldn’t keep a grizzley bear, a bison or a cougar. There are fewer injuries and deaths annually from these - considered the most dangerous of north american animals - than from pit bulls.