I do agree that it's more treatment than breed that defines behaviour, but, size, strength, bite and breeding history are all relevant.
Badly treating a tea cup Yorkie is not going to have the same potential concequences as doing it to an XL Bully. Size and strength are a huge consideration as to what the dog is capable of.
But so is breeding, we breed traits in and out of dogs (and horses, cats, sheep, cattle) to what is desirable. Unfortunately in the case of bull dogs, part of the desired trait was enough aggression to take on an animal many times it's size without hesitation and latterly the aggressive behaviour that is sought in dogs used as ego penis extensions. The aggression has been, and continues to be, bred into these dogs.
It doesn't just happen with temperament either, look at the dogs who've had basically, deformaties bred into them that cause physical issues because it's seen as a desirable trait of the breed.