Any dog can be aggresive, but IMHO, the WORST dogs are the small terriers!! My folks had West Highland White terriers and they were horrible!! They attcked anything and everything...no fear at all.
You are absolutely correct, all dogs can be gentle, it's matter of raising them properly. We call our pit-x Hunter because he looks like my father-in-law and myself when we put on our camoflage...He looked like he was wearing Tiger Stripe fatigues to me when we rescued him from the pound. He's a big mush pot with those who know him, but he's VERY protective of us, especially my wife.