We'll see if you say that when you've got a rat or mice problem. They were bred for a purpose and a damned good one. If not for dogs (and cats), we'd never have been able to sustain an agrarian society. My dad's cow dogs often made the difference between profit and loss by the end of the year. They were well-mannered and quiet, but would have torn your hand off if you'd done anything to threaten my dad, his property, his livestock, or his kids. But those kinds of dogs deserve big homes; folks on small properties owe it to their pets to have small dogs.
If I was going to have a dog, there's a good chance it would be a JR -- aggressive, nasty, and as metmom says, small enough for anyone to drop-kick across the room if need be.
BTW, I have nothing at all against JRs. A friend has them and they have always been well behaved. They’re great watchdogs because they make enough noise for any 10 other dogs when someone approaches. She doesn’t take any nonsense from them, though.
That said, if I were to own a dog, I would not likely get a JR. The energy levels are way too high for me. They have springs in those legs and know how to use them.
Yes, little dogs can be aggressive and there seems to be a correlation to that and size, but a smaller dog I could defend myself against. A pit is just way to strong and unstoppable for its size.