
I personally think what you have described DOES sound like fear based aggression.
A happy, confident dog doesnt need to use aggression, but a fearful one will get in there first in a lot of situations to tell other dogs to 'back off'.....
The example you give, of a person saying hello and then smacking you int eh face, is exactly how i would describe my dog Rocky, when he is on a lead.
If Copper has been kept crated and undersocialised as a youngster, then taht could well be the grounds for dog to dog fear aggression.
He hasnt got the knowledge of other dogs body language, he isnt confident around them, and has he ever been attacked by another dog, or even just made to feel uncomfortable/threatened?
This can become a learned reaction, but until you remove the reason for the fear, you cant begin to 'unlearn' the reaction.
Hope that helps
Em