There should be formal training for people who want to own a dog larger than a certain size. The number of negligent owners is astounding.
The people who own large aggressive breeds rarely cross over with people who know or even care about training.
Or worse they purchase them for protection and train them to be aggressive then neglect them.
Training a large dog to be obedient and highly controlled in a good way is A LOT of work and expensive if you go through classes to do it. However you normally end up with a highly reliable and predictable dog.