[maybeiloveyou]

Actually, the tail can wag even when he's angry, it doesn't always mean that his barking/growling is friendly. It's unlikely that another dog would not know if he was being friendly, because dogs pick up on these things very quickly.


Can you take him to socialization classes? Those are usually for puppies, but even if he's a little older, he might be more calm with a puppy. Usually dogs get aggressive due to territorial/dominance issues, and with a puppy that's not a problem because most are submissive.

Then you could move him up to socialize with a bigger (but friendly dog), like a golden retriever or something. He's a little older so the socialization process will take longer, but it can still be done. Good luck!