WorkingInSTL

I am going against my own policy of giving an internet diagnosis of a canine problem here, but what I have heard is common of a puppy at 6 months. The dog is most likely in the "fear period" of his development, and feels threatened by strangers. That's why you see his hackles raised, etc. A 6 month old puppy does not have the courage to face a percieved threat, so he will naturally back up if he feels he is being confronted directly. When the "threat" turns to walk away, the youngster perceives that as having won the challenge, because in his mind, his bluff made the person submit by retreating. This behavior should definitely not be encouraged, and you run the risk of it getting worse if not corrected.

I do use the "alpha roll", but only to correct a very specific behavior, and only with dogs of a very narrowly defined temprament. In other words, I have a use for it only to correct a very specific type of dog with a very specific problem. Due to the age of your puppy alone, your dog does NOT fall into this category.

I think you need to find another trainer to work with. This behavior, as I've said before, is VERY common in puppies the age of yours, and this trainer should have recognized it right away and known how to deal with it appropriately.

I stand by the method I gave you initially to correct this problem. A pop with the prong collar is appropriate for this misbehavior, but as another poster pointed out, be sure it's stern enough that your dog is very clear that you will tolerate this behavior. That, combined with the concept of handing the leash to other people and walking away, teaching the dog that other people are "fun" and not "scary", almost never fails to solve this problem with puppies, expecially after they grow out of the awkward stage of mental development that your dog is probably in right now.

Edit: I'm not a big fan of the spray bottle. If he responds to a leash correction, I would personally stick to that. To me the spray bottle, or marbles/pennies in a can are just a gimmick and really does not address the problem, except to create another one (for example, the dog is conditioned to be sensitive to water, so the next thing you know, it doesn't want to go out in a rainstorm, or you've made the dog sensitive to loud/strange/unexpected noises). Others will disagree with me, and that's fine if these methods work for them, but, for me personally, I've seen just as much negative as positive with these sort of trainnig methods.