I don't know if one or many of these factors is having an impact on his behavior today, but I want my sweet puppy back. I want him to be able to sniff and greet other dogs on a walk without having people recoil in fear. It's the people who are scared (rightfully so). The dogs know that Baxter is full of shit and is only exhibiting this aggressive behavior because he is scared or excited. He's never hurt another dog or human.
And that's what I think it is. I think it's a combination of him being scared and excited. I did some reading last night about what to do with a "leash aggressive" dog. Besides calling Cesar, the options seem to be to avoid or distract. Avoid being don't walk your dog around other dogs (who wants that?) or distract your dog around other dogs with treats, toys, etc. I'm going to try option 2. I bought a clicker last night and have been working with him on simple commands (sit, down, come, look), and he focused on me really quickly. The next step is to take him to a park where there are dogs in the vicinity, but not too close and practice the "look" command (look me in the eye), using the clicker and treats as rewards. I'm hopeful that we'll make some progress with this method, but we'll see.
Has anyone else had to deal with a leash aggressive, but otherwise awesome dog? How did you deal with it?