Your statement that this isn't reality is very much correct. It is however a ghost if you will, that is trying to haunt him and force him to believe in the past experience as a determining factor of his future. Lots of people do lots of things in this life. He has chosen to trust you with this painful secret. Thank God that it is out and you are now both moving forward from here. If it helps, think of it as a gunshot wound that he endured as a child that he never showed you. The scar is there, it's ugly, it's not caused by you and he is still maybe a little uncomfortable if he moves or twists a certain way. The healing inside his true tissue is what's at stake. Be there for him in this matter and you will have a friend for life, I promise.
The absolute best to you and yours, Dewey