BTW size isn't everything. I've got a terrier. It's got a hard, locking bite, it's powerful next muscles can really rag other animals around and it's got a very high pain threshold. I mean it's a terrier, they're tough and fight their corner. It's a heavy one at 7.1kg fit weight but once got up to 9.5kg. It's a border terrier and would see off a labrador, in fact it has!
Our dog is capable of more harm than a much bigger dog but it's not got the temperament to attack unless severely provoked. Even then it is smart enough not to actually want a fight so uses dog communication of noise and fury without serious contact.
As to my expertise. I'm an expert in my dog and my dog only. I understand it and it understands me. I have a good understanding of the breed having met hundreds over the years.
I have never met an xl bully only read up a bit on them. As such I have a healthy level of wariness about the breed but do not know what the best solution to stopping dog attacks by this breed or others.
I am confident that my dog will not be among those dogs who attack people. I believe that because of the way I raised the dog from a puppy. All this makes me suspect the real solution will be more about the human owners than the breed or type of dog.