It can be said of the former as well, with highly prized hybrid strains of, say, tomatoes with strictly controlled patented seed supplies; the plants do not bear true (being hybrids) so trying to harvest seeds from the fruit itself doesn't help.

For example, I like the kumatoes from the grocery store, but I can't grow any myself, and probably never will: https://en.wikipedia.org/wiki/Kumato

Hi there! Just joined yesterday myself.

But you're not being accused of drugging and raping several women over a period of many years

Or so you assume... :) Although, for the record, I'm not. To the best of my knowledge.

But giving your wife a couple of glasses of wine isn't quite the same as giving her a glass of wine with three half benadryl pills, which in turn isn't the same as luring teenagers into a beer-van.

Which is precisely my point. Giving a consenting and willing adult drugs does not "establish a procilivity" in any meaningful way towards using drugs on unsuspecting women to take sexual advantage of them. They are not "the same."

Recreational benadryl is a thing. Getting as far as typing "recreational diph" went ahead and autofilled with "enhydramine dose" in google, same deal for trying recreational benadryl. Anything psychoactive is going to find someone willing to use it. Honestly, benadryl's not infinitely far off from quaaludes, in that they're both powerful sedatives, so if you can stay awake through the hypnotic effect, you're going to have odd experiences.

http://www.urbandictionary.com/define.php?term=diphenhydramine

but I suppose it establishes a proclivity for placing drugs in women's drinks for the purposes of having sex with them.

With the, err, rather important bit that he does it with women who are willing to take the drugs. I pour my wife a couple of glasses of wine on a romantic dinner -- that really doesn't mean that I'm luring teenage girls into a van with free beer. "Establishes a proclivity" is a terribly dangerous concept precisely because it can be so tenuous.