It sounds like you have a submissive peer on your hands. This has nothing to do with potty training and he can't help it. It's a fear thing and it's something in the dog. All you can do is try to manage this by not looking him in the eyes, letting him come to you for petting and not looking at him when you do, don't grab him by the collar, and learn his other triggers so you can either avoid them or do them outside where it doesn't matter. There's still a chance that he might grow out of this, but I wouldn't hold my breath.
Do a search here for submissive peeing and you will find a lot of threads on it.
Elaine and the herd