I think the dog owner needs a license, not the dog. You can have small little nasty little dogs, or big dopey fun big dogs. All dogs get angry, and all dogs can and will bite. The difference is, if a pitbull bites you, you know it. There isn't anything particularly mean in the species, its been bred out.
What has been bred IN on the other hand, as trash people raising massive dogs in little cooked up apartments, not feeding them properly, not taking them for runs, and not know how to raise a dog.
you shouldn't be beating your dog with a stick when its a puppy. So yeah, license ethe fucking dog owners before the dogs.
*side note: We bred and raised dogs growing up, mostly cockers, never pitbulls, but the fundamentals are all the same.