Tracey, Species is a paper classification. It has no basis in reality. Genetics are a sliding scale, not boxes on a chart.
Dogs are classified as one species for historical purposes. It was assumed that if you could interbreed, you had to be in the same species. This is since wrong, Dogs are no longer truly one species simpley because you can interbreed.
Tigers, Lions, Leopards and Jaguars can all interbreed, they are not one "species" (again a paper term, genetics are a sliding scale not a set of check boxes in a tree formation).
Likewise, you can mix a domestic cat and lynx or bobcat in the laboratory, no one has tried with Puma (for size reasons it would probably be fatal). Thus if we still applied the concept of Breeds in the same way we do for dogs then a Puma, Lynx and Bobcat would all be the same species.
We don't for obvious reasons. And realistically, all dogs are not "Dogs", despite being able to interbreed a german shephard is really a different species than a rottweiller which is a different species than other animals.
And your missing the point on the Dangers of Pittbulls, its not Jaw strength thats dangerous. Jaw strength (unless you are very weak such a child or elderly or a very petite man or woman) is not a big issue, it may hospitalize you, but it won't kill you.
Pure body muscle. A pitbull is all muscle. Even with a Muzzle on a Pitbull could easily kill someone with raw muscle power.
There is no reason to own an animal that deadly no matter how cutesy you think it is. Bears are cute and intelligent too, and far more docile. Right up until it spooks and kills half a dozen people.
And not all dog species have been domesticated as long as elephants. Some are far longer, some have not been.
Quite frankly, domestication only matters in terms of suitability if the animal has been bred to BE passive. Fighting dogs have been bred to be specifically aggressive. Its the same reason why cats have not become docile despite being domesticated for over a hundred thousand years. They weren't bred to be docile, they were bred to hunt rodents. And that means they get twitchy, and after purring and wanting to be pet, at a random moment they tend to just snap and claw at you then skitter away. Many cats never do this, many well trained and cared for cats can't help but do it.
No matter how cutesy you think Fighting Breed dogs are, they will do what they were bred to do. Even you can train them not to (and you can, same as you can with a bear) they are too dangerous if you don't train them properly.
In terms of power, a German Shephard and even a rottweiler (though they are pretty damn strong) is nowhere near the power of a pitbull, which can kill or seriously injure someone with a muzzle still on.
Your logic that it is somehow wrong to ban one type of animal if you allow another type is absurd. You want an inquisitive dog? there are many, you don't need one that can run through an average hollow house door (and I've seen it happen when someone opened up its treat bag just as someone else was slamming the door, although it was pretty damn funny)