You misuse a term: Sex is not a basic body function, but a secondary one (part of the reason you don’t understand sex, because you don’t understand its place).
Basic body functions, by definition, are those required to sustain one’s own life: drink, eat, digest, urinate, defecate, breath...kids are born knowing how to do those things.
Biology 101: Eat, survive, REPRODUCE!
I’m guessing you encouraged your son to become an engineer without bothering to learn math?
Actually he IS training to be an engineer and he KICKS BUTT in his AP math courses.
If your teen sneers at conservatism - you shouldn’t brag about how you raised him.
My son is fairly conservative - I have raised him well.
Just answer me this: why does teaching abstinence work for cigarettes, but not for sex?
A nonsmoker does not crave nicotine. Sexually, a teenage boy is like a three pack a day smoker who just quit cold turkey. They WANT IT.
If you wish to teach your kids that they should hold off on sex until they are married that is your business. But they should still have an understanding of how the body works and the potential risks involved with sex.