Folks are often surprised that their Puppy Culture-raised dog is not indefinitely tolerant of every sundry dog it meets. This flow chart on "normal" dog sociability from Cindy Bennett Martin is the BOMB and clarifies what's normal, even with excellent socialization.
As so often is the case, the problem lies in expectations - we expect dogs to stay on the left hand side of this chart whereas in reality that is highly unusual in an adult dog.
They are almost always going to move to some degree to the right, no matter how excellent your socialization and rearing plan is. Listen to your dog and give him what he is asking for!
