I agree with babigirl & Igmuska. I'm confident that the EM was challenging your CC. I further offer when your son went to help he escalated the situtation in the CCs eyes. Dogs do so much sutile communication with glances & posture that even very experienced handles may miss it if they are not watch carefully. Chances are that the "Insults" started the minute these two saw each other. The good thing is now you know your CC will not accept being insulted by other male dogs. He is young enough and fortunate to have experience owners. I would concentrate on this issue now before it escalates.