Big mouth Boxer

OK, I am having some issues with Cooper and am starting to get frustrated. He is not a big barker in the house unless we are playing and I am letting him bark and "sing" and be silly, but he will hush on command.

When we are walking and he sees another dog, it is a different story.

He is just acting like a tool when other dogs are nearby a lot of the time. I walk him a lot in our neighborhood (dogs everywhere), at local parks and hiking trails, and also on the walking trail to pick my son up from school and he will get to where he wants to just bark, whine, and carry on when there are dogs I will not let him greet or play with (several of them we are friends with and he will get to sniff and play with a bit, but others we do not know and I don't take chances). I never let him 'get away with' acting a fool, and do my best to anticipate if he is going to bark at a dog so I can correct him (just a eh-eh, or a sharp shhhhh type sound usually works well) and sometimes a hand near his face. Obviously not hitting him, but making a "stop" motion in his line of vision to distract him from the barking, along with holding the leash firmly at my left side to make him stay where he is supposed to be. We always keep moving and I praise when he is quiet. I am totally in control of him physically, but I need him to shut his mouth and act more civilized because it is embarrassing to me and obviously not something I want him to be doing when we go places!
I am obviously aware that a lot of this is his typical, boisterous Boxer personality (this is the third Boxer I have owned in 11 years) but I am just getting frustrated with his reactivity to other dogs and I can't have him essentially trying to throw a tantrum when I won't let him get to other dogs. I need him to walk by calmly. Any tips or methods to work on this would be greatly appreciated. Thanks.