Thanks for the advice Gary. I went out looking for some help and was referred to a trainer that's also a behaviorist.

He told me that he's seen that protective nature with people but never with another dog. He really didn't have a viable strategy besides introducing people and dogs separately. He's supposed to be doing some research for me. He also said that the only time he's seen a male act like that is when a female is in heat, but it's not normally towards people. It's mainly towards other dogs. 

I had my son help me do what you suggested about the walk. I can control him on the walk and have been able to do corrections. I'm guessing that this is going to be a lengthy endeavor.