I took my dog to my friend's house. Mistake. They had family over and a red-zone aggressive dog with them. She attacked my dog multiple times over the course of a day and a half. He is very good natured and recovered right away when they were separated. He is a service dog and has never exhibited aggression before. This morning the puppy was trying to climb over his back to get to the kitchen and he jumped over and snarled. He did not pursue her, so his reaction was a startle response, not a purely aggressive reaction. He behaved this way consistently when tested. I am left unshure what to do because I cannot responsibly take an aggressive dog into public. How do I go about addressing this issue?