Yeah, I’m with Amber – if you’re tense or stressed the dog notices, so if you tense up when you see another dog or another person on the street, the dog will learn that other dogs/people are to be feared.
My dog totally failed out of obedience classes (he wanted to meet the other dogs SO MUCH, he kept barking and wouldn’t listen to me) so now we’re doing private lessons and I’m trying to find him some friends to hang with. I don’t know, socialization is hard . . . I guess you just have to keep trying your dog with different playmates until you can find one who’ll tell your dog to back off when he’s being rude or rough.