Johnny does not like other big dogs--he would play with all the little dogs if he could! He snarks at dogs who take too long on the greetings, I kept him muzzled during BBH. I did consult with a dog trainer, she said he was telling other dogs to back off in dog language, and to keep the greetings short as possible and PRAISE and reward if he got sniffed and didn't react. Also, we kept him and Momo and Spirit muzzled when we had to stay with them, irritating for them, but it kept everyone safe and mostly snark free!
I also asked an animal communicator why he didn't like other dogs, she said he saw another grey get attacked and pointed to the shoulder that bothers him--go figure.