I don’t buy it. Different breeds have different characteristics bred into them and it has nothing to do with how they are raised. A golden retriever is born to fetch. A bloodhound is born to sniff. A cattle dog is born to herd. Pit bulls were nice dogs 50 years ago but now the breed has been turned into something wholly different. It would take another 50 years to breed the aggressiveness out of them again. And that will never happen because they’re too many gangbangers breeding them to be aggressive.
Depends to a degree on the breed and also the breeder.
But A well trained dog will behave despite the breed.
Years ago I had a girlfriend who got a St.Bernard as a rescue animal. Initially “Snuffy” seemed to be a sweetheart. She was very attentive and affectionate. But some unpleasant characteristics started to creep through. She didn’t like men with dark hair, men who wore sunglasses or glasses with black frames, and (especially) blacks.
We put her through obedience training and she did well, and we could leash her up and walk her but she had to be watched like a hawk. After she snarled at some kids I made sure not to let her be around kids at any time. After she lunged at one of my brothers who had come to visit (she leapt through a plate glass window to get at him) I put her down.
I was told by a vet that Bernards had gone through a period of popularity and some unscrupulous puppy mils had bred inferior dogs in an attempt to cash in.
It’s not only that. Pits bite and don’t let go, they’ve been bred to do that. So maybe owner get lucky and their dog never has a break and bites. But if it does, it’s more likely to kill.....