there are two things here - the manner of communication, and the content of communication. you only have control over the manner in which you communicate, and how you can expect him to perceive your method of communication. As long as it is respectful and considerate, you are in good standing before the Gods of Etiquette and Kindness. you don't have any control over how he will react to the content of your communication. if you express (dis)interest, he might want just the opposite and react to it with some form of sadness. You have no control over mitigating such a response - so just stink it up and deliver the message. If your message causes him unhappiness, there is nothing to prevent him from also recognizing the fact that you did so gracefully and kindly - and that will only make him thankful for your tact. If he can't see it, then he is clearly woolheaded and you will be free to feel vindicated.