I think Kaedyn's fear aggressive. He lunges at men while on walks but is normally pretty timid around them. He was so scared of the vet today.

What I've been doing is rewarding him for not growling or lunging. I made the mistake of correcting him and Cali's right, it's the worst thing you can do with a fear aggressive dog. From the dog's perspective, they already see (whatever they fear) as a bad thing. If they get a correction everytime they see that thing, they're going to associate that thing with the horrible corrections. So instead, Kaedyn gets treats everytime he passes someone and behaves like a good boy. If they stop to pet him, I get them to offer him treats as well. It's been working pretty nicely. He still growls now and then but he's 100x better than before.