As a vet tech, I can count on one had the number of large breed dogs I've had to muzzle. I can not even begin to count the number of small breed dogs we need to muzzle. The point being is that owners of larger breeds, such as pit bulls, do face more responsibility because if "bad behavior" such as mouthiness or jumpiness is allowed to go unchecked with a larger breed you face much bigger problems than if the same behaviors were left unchecked in a small breed. So we see many, many small dogs coming in that need to be muzzled versus larger breeds that are perfect angels at the vet.

The point I'm trying to make is that it is 100% the owner and in how the dog is raised.