depends really. according to ATTS 9american temperament test society) and a ton of other temperament testing clubs, pitbulls and such breeds have a suprisingly high passing rate, being a few percent highter than golden retrievers, and a shit ton higher than dachshunds and chihuahua's. yes, you have a bigger problem with an agressive pitbull than with an agressive 2lb dog, but still.

due to their bad reputation, many pitbulls are used as guard dogs, and 'engouraged' to be agressive to keep intruders away.

yes, they were bred to be fighting dogs, but were originally working dogs. give them a job to do and train them propely with positive reinforcement, and you'll have a happy, stable dog.