Dear Michael,
I would like to open, saying how incredibly difficult you have made my life. Accepting your apology would be very hard, even now. I would like to say I could forgive but not forget, though that would be a lie because I cannot forgive you.
I haven't told any more people about what happened, not because I'm scared or ashamed, but because it just isn't worth mentioning anymore. Besides, it was a long time ago. What was an enormous problem then is history now.
I still think about it sometimes, when I'm with other guys. It ruined that experience for me, and nothing anyone says or does could erase that for me.
I think about you sometimes. You were a nice guy, you seemed like a nice guy. I guess being nice and holding doors open for people doesn't stop you from doing terribly wrong things. And making other people frightened and scarred.
I respect what you're trying to do, and I would never try to exact revenge. I just can't forgive you. As much as I'd like to be that nice of a person, I'm not. You did something irreversible.
But I really am sorry that I can't forgive you. I've spent a lot of time in therapy learning how to be angry and then how to be forgiving. But I'm just not there yet. I'm really sorry.