That is bull. Pitbulls do have more of a predisposition to attack than most breeds. Not only that, they were bred to be fighting dogs, prized for their strength, aggressiveness and instinct to keep fighting until either they, or their opponent, was dead.
Yes, I know there are other aggressive breeds that will attack. The difference is that other dog breeds tends to bite you to get you to back off. A pit bull will attack you, and keep up the attack as long as it can, completely mauling their "prey."
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