Some pretty good advice in this thread already, figured I could give you some additional perspective on this:

Your story reminds me a lot of my partners story. His overly conservative parents essentially destroyed every aspect of his life attempting to force him straight before kicking him out when they realized he wasn't going to change for them. Since then he's had to completely restart life twice now (the second going so much better then the first, mind you) he was sleeping on the street for a period of time... He's had a much harder time going NC and has to deal with them every now and again and let me tell you, over the years nothing about their attitude has changed. They think that since he is dating a woman that they've succeeded (bisexual, if that wasn't obvious. They only focused on the fact he was with a man.) They do not in ANY way acknowledge who their son is, what they've done to him, and it seems they've forgotten the whole thing and now blame their son for putting the distance between them.

We've had many many talks about this, and I could pretty confidentially tell you the only thing that could ever attempt to make peace between my partner and his parents is if they fully acknowledged their mistakes, and made an honest apology and made absolutely no excuse or justifications (as is their common tactic) and then at least attempted to accept who their son is, and accept that they could not have done anything worse to him in that time in his life.

I would also let you know, that if all that happened he would forgive them, but that's about it. He would still request they have no part in his life. If you do reach out to your son, just be willing to accept that no matter how much you apologize or how sincere you are, your son may still want to be separate from you, unfortunately.