I understand from a vet friend that there is a gene that, should the dog have it, that dog is prone to seemingly out of the blue rage attacks, and the xl bully breed suffers particularly from that as one very prolific sire called Killer Kimbo had that gene, and many dogs around today are descended from him many times over. Not the only breed that often has that gene but in other breeds any intact animal whose offspring showed signs of sudden rage would not be veed from again, nir any of the offspring, apparently there wwre some Labrador retrievers who descended from one dog who had it, and there was no more breeding. Responsible breeders won't breed from dogs who have traits like this or other genetic problems, eg PRA, which causes progressive blindness, if a dog is a carrier a responsible breeder will test for it and if he carries that gene will not breed from him
Against this there are breeders who breed xl bully dogs for looks, massiveness a s suchlike, who accept aggression as a part of what a fighting dog does
So many of these stories are to involve a sudden unprovoked attack by a dog who has been ok until now
Some are no doubt owned inappropriately, ie the dog is not exercised enough or is passed on from someone else, and is not really a happy dog, some that do not come out of the blue can be people not recognizing the signs that a dog is getting irritated, and try and stop the dog growling, or doing that thing they do lifting their lip to show their teeth, both signals from the dog to back off because they need some space, so the dog feels like it has to show its feelings in another way
Plus they are very big and .muscley and a small child is half the size, if someone is sitting down their face is attack height. A friend who lives in London said that some people keep an aggressive dog as it's not illegal as carrying a knife is
Nobody needs a huge musclebound dog bees for fighting, breeding should stop, all such dogs should be neutered, and importation of that sort of dog banned, which yes is not easy, and we can't tell other countries what to do but we can tell them we don't want potential killers coming in
But that doesn't address the immediate problem. I've no doubt that some are big softies but how so you tell if yours is one that has tendencies to fly into a sudden unprovoked rage until.it is too late