The social deprivation, the ‘deed not breed’ or ‘owner not dog’ and all other arguments are irrelevant.
Nobody should be allowed to keep these sorts of dogs as pets and, like a pp said, the dogs should be taken away and destroyed. There are other breeds and types of big dogs that should go with the XL Bullies.
The issue is more or less exactly like that for firearms. It doesn’t matter how responsible some owners are. If any owners aren’t responsible people are injured and killed. Often children.
There is no justification for keeping a dog capable of killing an adult. None.