You didn't mention in your note the context of the discussion held with your son, and I'm not making light of your concerns. But I can assure your son is not innocent with respect to such matters. He's heard the street version of these things already. If you haven't discussed sexuality with him and/or made provisions for him to discuss questions he might have with someone you both trust, then you've done him a great disservice.
I may have the wrong impression but what I hear in your post is a hysterical Mom afraid her baby is growing up. He is with or without you, Make sure he has the tools he needs to grow up as well rounded young man.
Now as to the dubs seeming obsession with sex. I think that many of the older dub elders have been equally hysterical about sex. Obsessed with wanking, kissing, hand holding, telephoning, and anything else they can think of that might possibly be a link to SEX! The enlightened elders I know are much less occupied with such mundane things.