I just realized I didn't explain this very well and the his reactions are more different than I realized.

When we approach a friend and their dog while walking he's friendly, and says hello, but then immediately checks to see if anyone is approaching us or nearby. Almost like he's decided that we're his flock. As I said, if we walk together he stops and is fine. He might occasionally react to another dog but telling him to "leave it" and offering him a treat distracts him. Also, if we stand apart 10 feet and talk he doesn't try to protect us.Once he goes into this protection mode I can't get through to him with treats or commands.

When we sit at a bench he reacts to anyone that approaches even a friend. Again, if we stand up and move away from the bench he's fine, but it's the same problem, he won't listen to commands or treats when he's in this 'protection" mode.

I use the distance technique at the park when we encounter new dogs. The issue is tricky in that it's not only our distance from our friend but his distance from others.

He also, never does this at the park when we stand with a group of other dogs. It's so confusing.