Dog aggression, dog to dog?

This is a complex question, and I have found that some dogs, just can not be left off lead. Unfortunetly some dogs are just aggresive by nature. Is he neutured? What type of breed? It seems that his instinc is too strong to listen to you when called. He is obviously fixated on the other dogs. Usually male dogs that are dominant and unneutured, do challenge other male dogs. I would really stick with on the lead training for a while, and if he is not responding to you, you will have to make peace with the fact that he is just one of those dogs that need to be kept on a lead at all times. It is not a bad thing at all though. Also, give yourself some time. He is still new in your family, and probably unsure of how to react to your commands at this stage.