I have to agree with Tannji, it depends on the owner. My wife and I have rescued, and adopted dogs for 15 years now. The temperment of any dog is usually dependent on how the owner raised it. You can have very freindly pit bulls, dobermans, shepards, as long as the owner socialized, and raised it right. Sometimes there are dogs you just can't help, they need to be put down.
Tim, the way you trained your son is very important, and smart to do at a young age. Also never extend your hand out palm side up with fingers extended, one chomp and you loose a finger. Always as a fist, palm facing down. Once the dog sniffs, and everything is ok, then extend fingers.