Pitt bull's aggressiveness are a result of the humans breeding or owning/training them. Any dog can make mistakes, but the nature of pit bulls jaws and mental determination means that when they make 'mistakes' they make big mistakes. I strongly believe that the type of owner who is attracted to pit bulls or rottweilers or whatever big scary dog is the kind who encourages that kind of aggressive behavior or who is not qualified to train them properly.
That being said, a nervous frightened pit bull can be one of the more dangerous dogs at the animal hospital I work at.
ps. Canary dogs are pretty badass
