Thanks for the useful analysis, al2simon.
In honor of the original thread topic, I would like to post what I personally would tell a son about consent, if I had a son. And before I start, yes, I am a charter member of Overthinkers Anonymous.
So, first, I would tell my son that my genealogical research on our family (at hobby level) has shown me how much we are all embedded in our historical context, without being really aware of it. I don’t know that I would exactly call it the “forces of history,” but people made decisions which seemed like perfectly rational, independent decisions (to them) at the time, and it is only when it is viewed through the longer lens of history that one sees how much they were acting in according with historical or cultural movements. I have even seen the historical forces acting on me, since enough time has passed to change the milieu. Then, I would say that my research has also shown me this: anything that our society permits to happen–to anyone–will eventually happen to someone they love, or someone they would have had cause to love, if they had lived contemporaneously. Accordingly, we should do whatever we can to prevent harm and injustice, both.
Then–provided he is still awake–I would talk about the societal circumstances that exist now, and the changes that have been rapid on the time-scale of human adjustment, legally and socially. (This was alluded to by another recent poster–sorry for not providing a specific reference.) In a past era, the default assumption about a random college woman’s willingness to have sex was “probably not.” This has now shifted (in my view) to “maybe.” This creates complications on both sides, and I don’t think that university policies have caught up with it. There is the problem that women can be raped by men who don’t realize that they (the men) did not gain consent. There is a smaller number of men who realize they don’t have consent, but think it is likely that they can get away with rape, because the presumption of a hearing board is not going to be “no,” it’s going to be that there needs to be proof of rape. (And appropriately so.) Some university policies are aggressively crafted to counter this. The point of this part of the discussion would be to try to explain how universities have reached their current stance, and–I would hope–to counter support for the anti-feminist backlash, which does exist.
Then, much more personally and driven by ethics, rather than by policy or political climate, I would tell my son that I still prefer chastity before marriage and fidelity afterwards. But I seriously believe that this is a decision that each person needs to make for him/herself. I would say fairly emphatically that if my son did not know a woman well enough to know whether he could trust her, he definitely did not know her well enough for sex (no matter what he had decided). Finally, I would encourage him be aware of situations in which a woman he knows might be vulnerable to a non-consent situation with some other young man, and to do his best to protect the woman.
(Hypothetical QMSon would probably stay with me through all of this.)