A friend had this same issue when walking her dog-he would go crazy when he saw another dog. She had him sit whenever she saw another dog coming and treat, treat, treat until the dog passed. And then "good boy". This way he associated other dogs approaching with good things. And guess what? It worked!
YES that is exactly what we have done for over a year now!! IF I am prepared and can get her FULL attention on me in a sit stay, the other dog can just pass on by. Although ONE bad encounter sets us back MONTHS. sigh... some dog owners think, oh LOOK a cute dog sitting, let's go say HI... roar.