I apologize that this response is so late, and I hope that this information will be helpful to you, and to others who may read your post.
While the interests of your friend are distressing to you, they don't appear to actually be fetishism or voyeurism. Fetishism does focus on inanimate objects, but the intensity of the focus disrupts the person's usual level of functioning. Your friend appears to function well within normal limits in public. Voyeurism is the term that describes viewing actual live sexual activity, generally in a secretive manner. Your friend's preferences may be an aberration from what you would consider normal, but they fall within practices that are not usually considered pathological. If your friend openly has shared his pornography with you, he has given you the opportunity to tell him of your discomfort with the subject matter. Discussing it with him would definitely be the first step to take, if you aren't able to accept his habits. If you have discovered the pictures without his permission, he may believe that his privacy has been violated. After talking with him about it, if he is concerened or feels shamed, he may benefit from talking with a therapist to help him clarify his feelings and comfort level, and make changes if he desires to do so.
Good luck to both of you.
Faye, RN, MSW