I had a situation like yours, and wrote about it here if you want to read it. These situations are almost exactly the same, in that we were both trying to bring information to our partner to make the right (in our eyes) call.

In my thread, half the forum members thought my partner was too uptight about hearing my opinion on the play, and the other half thought I should have left the decision in his hands. It seems to me like the same thing has happened in this thread.

However, you are the assignor. You are in charge of setting expectations for those who work under you. As far as dealing with this guy: be direct. Tell him that the officiating crew is a team, and their goal is to get plays right. If your partner has information he thinks can help, he should present it. It is up to the calling official to decide whether to take it or not. The key is being humble enough to listen to his information, opinion, and/or criticism.