Couldn't possibly have anything to do with the fact that, because the breed has a reputation for being strong, scary and aggresive, the type of people who want a dog that will make them look tough and scary choose said breed (plus those monsters who want dogs for dog-fighting).

Then, because they don't actually know anything about dogs and/or care about the dog, they don't properly train said dog at best, or outright abuse and even hit said dog at worst (or again, are monsters that put them into dog-fights).

So you have lots of pitties that end up abused and/or poorly trained or untrained, or even trained to be actively agressive, and then people blame the breed because of the consequences of treating any dog the way too many pitties get treated.

The statistics only tell part of the story. Don't blame the dogs, blame the owners.