German Shepherds, Staffies, Rotties, Dobermans. They're all capable of killing an adult but rarely do you hear of anything. It's only recently the XL has been targetted for some reason, and most of the XL bully attacks are more than likely similar breads but not an XL bully. If owners have control over their dogs there is no issue. If your dog has bad recall, don't let it off lead. If your dog is nervous, don't let it off lead. If your dog is aggressive, don't let it off lead. If you can't CONTROL your dog on a lead, don't take it to a busy area. If you can't trust your dog around people - don't let it off lead.
Bad owners ignore the most common sense of rules owning a dog.