Sure, they can be friendly. But you never know when they will turn on you and they can kill you. Yep but, Unlike a hand grenade, you'll never know when a pit bull has had its pin pulled until its too late.
Chihuahua's are MUCH worse temperament. The difference is that when the 6 lb Chihuahua bites you, they do it out of reflex and almost never break the skin.
IF a Pit Bull bites you they have the crushing pressure to break your bones and kill you.