This is such a contentious subject, however, as a dog owner of many different breeds over many decades and with welfare experience, I would say this:
My Newfoundland can SMELL water and legs it to the source as ITS IN HER DNA. She is also a stubborn pig when she gets a scent. ITS IN HER DNA.
My Newfoundland will be extremely concerned if I cry, or make a strange sound. ITS IN HER DNA.
My Golden Retriever, was a big soft melt, but he was destructive of tea towels because retrieving and being sweet IS IN HIS DNA.
My Cocker spaniel was pts as he was a resource guarder who bit anyone who came near him for a million different reasons (when I was a teenager) with no warning or predictability. RESOURCE GUARDING is a common problem in some badly bred spaniels.
My Pugs x 3 we're all the sweetest dogs around people but as a companion dog, ITS IN THEIR DNA. They are notoriously greedy again, it's in their DNA.
My Labrador is the sweetest most biddable puppy I have had yet and highly intelligent/can remember a command after only a few mentions. She likes to fetch and retrieve, again IT's IN HER DNA. She is extremely greedy, again, IN HER DNA. She loves water, again, in her DNA.
My foster LGD (Kangal x rough collie from Greece) was an escape artist who as a puppy could scale a 10ft fence, and wanted to live outside - as a LGD, IT IS IN HIS DNA.
Every single breed has traits. Unfortunately for XL bullies, their DNA involves a fighting/aggressive genetic. Yes, there will be some who are soft as clarts, it once they become status symbols in the wrong hands, they are a lethal weapon.
For this reason along with their size, they are simply not safe in the hands of anybody who can't control them in public. It should be illegal for children to be responsible for them and also every owner should have to pass a test on canine behaviour and breed traits. Furthermore, the inland revenue need to get their arses into gear and investigate every person advertising litters of puppies online. These people are making millions in cash, tax free, with no care who they sell their pups to and no fear of prosecution.