What you are describing is known as a "fetish," the sexualization of a non-sexual object or activity. If you look in the Fetishes and Sexual Fantasies section of these forums, you will find a ton of information. The Society for Human Sexuality at
Society for Human Sexuality has a lot of very good information on this subject.
From a clinical perspective, a fetish is considered a disorder only when it causes distress for the person OR leads to life problems such as law-enforcement difficulties or the violation of the rights of others. Otherwise, it is just considered part of the spectrum of human sexual expression, although it is beyond what is considered "normal" by most people. The American Psychiatric Association does not categorize it as a disorder so long as the person is comfortable with it and doesn't engage in behaviors that violate the rights of others.
Now, I know that's not what you were asking. You're wondering if something is wrong with your man that makes him want to do this. I can't answer that, and neither can anyone else, with any degree of scientific certainty, at this time. We simply don't know what leads to people becoming sexually aroused by non-sexual behaviors or objects. It can be produced by childhood trauma, but many people who have fetishes have no mental disorder or history of abuse or trauma. In this case, I can only say that "normal" lies in the eye of the beholder. The advice I give people with fetishes is to be sure to seek out partners who are comfortable with that activity OR to be willing to live without it.
There's no easy solution or answer here. I'm glad you and he are communicating about it.
Personally, this is an activity I would find uncomfortable and distasteful and I wouldn't engage in it. However, I'm not about to begin judging someone who feels differently. That is why we, the people on these forums, emphasize everyone choosing his boundaries for himself, but not judging people who have different values and who choose different boundaries.