Any dog can become viscous when improperly trained. We've had pits, rotties, shepherds, etc etc. They've all been the best dogs and not one of them has ever shown any aggression.

Currently, all together, we have two Cane Corsi (which I'm glad isn't a popular breed in the US because they are VERY dominant and need a dominant owner), a German Shepherd mix, two boxers, and a pug. They all get along great (that is when the girls aren't in heat) and aren't aggressive towards people. You can take toys away from them, you can take their food, you can pull their ears, and do pretty much anything you want to them. They WILL protect us, and they definitely have a creepy sensor. The Corsi and female boxer are all in protection training, but would never attack someone unless they felt we were threatened.

My mom has a pit bull and she's a huge ham. She's the most laid back dog you could ever meet. She doesn't even bark, and would NEVER bite some one. She might kiss you to death though! Once, a man in a taxi cab told me I should be careful with her around children because she might EAT THEM. I was like, "I don't know who told you that but they were dead wrong." He proceeded to tell me that his VETERINARIAN told him that. Way to give the breed a wrong name.

Again, any dog has the potential to become aggressive. Train the right and treat them well and the dog be submissive and will protect you all costs.