Why is this surprising??
They see sex in advertising and on TV. Their peers talk about sex constantly (at least, I assume that hasn't changed since 1989). It's "hot," it's "cool," it's what (seemingly) everyone who matters is obsessed with.
And THEN, unless they're really lucky, responsible adults who have had time to get used to the idea and learn to cope with their hormones (like parents, teachers, church leaders, friends' parents, et cetera and ad nauseam) deal with the issue by saying, "Don't talk about that! That's dirty! Keep your pants up!"
While "Keep your pants up" may, actually, be excellent advice...
...what you have is a community of half-grown people developing the impulses of adults but still possessing the judgment, reasoning skills, and impulse control of children.
Figuring it out, basically, on their own.
Do you have to be an Aspie with a liberal-arts education to be able to set aside emotion and social conditioning long enough to understand why, logically, this just isn't a good idea????
Doesn't seem that hard to me.
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"Alas, our dried voices when we whisper together are quiet and meaningless, as wind in dry grass, or rats' feet over broken glass in our dry cellar." --TS Eliot, "The Hollow Men"