It is difficult to know for sure. The look of enjoyment on his face possibly triggers a memory of something from your childhood that made you feel bad in some way, such as being exploited, used, objectified, humiliated, or something else.

The problem is that your mind is doing a good job, maybe too good of a job, hiding the actual memory, but letting you feel the pain of it - in the form of repulsion or disgust. Whatever is causing these negative feelings seems to be repressed out of consciousness, probably to keep you from being overwhelmed by it. I know this doesn't help, because you want to get to the bottom of this.

Do you have any dreams or nightmares related to this? Or any kind of recurring nightmare?