Thoughtful, and respectful. I appreciate the response.Maybe you should get a different trainer. It is unacceptable for your service dog to show aggression like that. I have couple of questions 1) what does your service dog help you with 2) did your trainer help prepare your dog for being out on the trails? A good trainer would have taken you and the dog out on trails and exposed him to likely situations before every recommending that you take your dog out on the AT. I am planning on taking our German shepherd out on a section hike in September and we are already teaching him to carry a pack with his own food and water. We take him out on trails and expose him to situations he is likely to encounter. We teach him how to climb over obstacles, not to drink out of water sources without permission, to leave things on command, to sleep in a tent, to come on command and most importantly we teach a friend command. A friend command teaches the dog to allow any person you say is a friend to touch him without showing aggression.A service dog is not a personal protection dog and he should be corrected for showing aggression towards another person. I think your dog is stressed because he does not know how to handle all the things that go along with being out on the trail.People of all shapes and sizes, packs and trekking poles can all upset dogs that are not trained to accept them. Not to mention all the different animals and scents he will encounter. Walking long miles each day and sleeping out in a tent or shelter is stressful to a dog that hasn’t learned how to deal with them. If you dog continues to show signs of stress or aggression towards other people it might be best to get him off the trail until you can do some additional training and better prepare him to be out there with you.