How do I train my two yr old Chihuahua to get along with other dogs?

I just adoped a two year old pug/Chihuhua mix. He's a sweetheart, and obeys me with almost everything, except for other dogs! The other day, he bolted around my house and attacked my neighbors pitbull! We have dogs that live on both sides of us and evertime I let him out to go potty, he runs to either fence and starts going nuts for the dogs. The other dogs are very well behaved and my dog really gets to them. Now my neighbors are irritated with me and if the pitbull wasn't on a chain, this dog would have been dead. That still didn't stop him. Now it's difficult for me to even let him outside. I want to be able for him to go outside while I leave so he can go to the bathroom outside, but I can't. Now everytime I come home, or even when I'm here, he goes to the bathroom in my house! This is the first dog I've ever had and I chose him because he was already fixed, and housetrained. Does anyone know how I can get my dog to calm down?! I mean really! Antagonizing dogs that would kill him in a second!? I want to take him for walks and take him to the park. I feel this dog is just going to be confined to my house, and I can't do that. Now I'm scared to leave him because I know I'll come home to a house full of poop. He's become more of a responsibility than my kids! He's a really good dog, and very loving, he just doesn't love other dogs.