I get what you are trying to say and I'm going to be honest and say that I'm not a behaviourist (but do have an interest in behaviour) nor a genealogist so it would be difficult for me to answer this with 100% conviction as I honestly don't feel I know enough regarding genetics in specific breeds. I do think they are dogs with a strong sense of protection (owner, property, self?) and also less likely to be able to be controlled once in attack mode (also due to size/strenght)
My personal view is that a large, strong dog is not more likely to be aggressive than a small dog (as I've said before in the thread, in my experience I find the opposite, but again this is personal experience and opnion), the thing is if a GSD, a Rottweiler, a Great Dane, an XL Bully etc goes for you, you're in trouble. And hence the need to breed carefully (and being done by reputable breeders who should show they have an understanding of the breed they are trying to breed, a breeder's license if you wll) and with behaviour in mind (do not breed from parents who are known to be reactive/anxious or too young to be able to assess behaviour/character, same way you shouldn't be breeding from dogs with know hip dysplasia/hernias/cryptorhidism and other unwanted characteristics that can affect health, both emotional and physical of the animal) and have stricter rules/regulations about who can own the breed and make certain things mandatory for pet ownership in general but larger breed dog ownership in partcular (ie muzzle training, third liability insurance, lead training and strong recall training, secure fencing etc, again an owners bootcamp if you will where you have to show an understanding of the breed you are taking on and how to safely handle it).
You have to take multiple lessons to be able to drive a car or use certain power tools but everyone can go out and buy a 40+kg dog with no restriction and no way to control if there have been issues before (neglect, backyard breeding, aggressive dog ownership etc). That is my own personal opinion and in my view a much more effective way to control problem dogs (but also nothing will ever be 100% safe and that's something we need to keep in mind as well when choosing a breed, they are animals at the end of the day, no matter how well trained they can always react unexpectadly for various reasons and that should be taken into account when deciding to share your life and home with any animal, ok maybe not fish).