Docshounds. I've never met a nice one. Even my mother's Dixie was mean if you caught her at the wrong time. And barked at EVERYTHING. I would never own another one. And don't get me wrong. I LOVED Dixie. Heck, she was the first pet I had when I was little, so I idolized her. But how that I've had a black lab (Killed.. sigh.. shot with a crossbow by some stupid kids) and a tiny little mutt my father in law gave me. (We gave her away when out house burned down. My neighbor was watching her for us and her autistic son fell in love. I couldn't say no) I will never own another little dog again.. or another big dog. Sadie is perfect for me. She's active enough to go on walks and hang out at the flea market, but calm enough to cuddle on the couch and watch TV. She's good with cats and kids, and having a disabled cat means I couldn't have a mean dog, ever, or risk a dead cat. And she never barks unless someone is around the house.. I never intended her to be a guard dog, but she's really good at it.
In short.. It wasn't the training, it was the dog. She was a good dog before I crate trained and leash trained her. She was a good dog as soon as we got her, and only got better from there. If a good dog can be born, so can a bad dog, and it doesn't matter the breed.
There's no way to regulate ownership of animals in a way that would keep bad dogs away from people. It's just not possible. Any dog can be bad. It can be born in, it can be taught, but breed doesn't matter. Singling out the pitbulls because they have the "Locking jaw" (-snort-) or because they've been bred for fighting each other (Not true) is like, as said before, singling out a race of people because members of it are violent. Dogs are as individual as people.