Being a lesbian, it's illegal for me to get married and thus double wrong for me to have sex. Of course if we're going by the same standards, then I'm already in so much religious trouble that no amount of shoveling will get me out, so I guess the point is ultimately moot.
I think, really, the entire religious argument (debatably, all religious arguments), comes down to christians hating fun. Take
blue laws for example. Example
here and we all know how to use the google machine to find more references. It basically amounts to "those young people are enjoying icecream! God fucking damn, I hate when people enjoy things!" and actually had a law passed to make icecream products illegal on sunday. That, in a nutshell, amounts to the christian mindset on pretty much all restrictions. "If it is good, then it must be put there by the devil, and is therefore evil." When I used to be dragged to church, I even remember one relative or a friend of a relative or the pastor, someone, I don't recall, said something like "this aint one of those fancy churches with the padded seats and arm-rests. We're real christians." I think a huge part of the push against sex is because it's a pleasurable act, and gets the knee-jerk reaction to be evil. I honestly think this is the entire reason for every anti-masturbation thing I've ever seen. If there was EVER an act that would be healthy, enjoyable, and safe, it would be masturbation. It 1: shows you're healthy enough for rigorous activity, and let's be fair, many aren't, 2: is enjoyable, and releases chemicals that elevate mood and curb depression/anger, and 3: actually causes a LOT of bloodflow to the brain, which in turn generates a lot more oxygen and nutrients flowing through the brain and that's nothing if not good. Plus, who are you hurting? The bedsheets? Your panties? (If you're a girl. Or if you're an inclined guy, I guess.)
There's always a big religious push against anything fun, and there's always a big extremist push to do only things fun. I'm not saying either is right, and really I'm exactly saying "neither is right".
BTW: Alabama sex ed was one 45 minute session where the girls went to one room and the guys to another, and we were showed a brief slideshow of female anatomy (I assume the guys were shown male) and then told a little about hygiene and regular showers. Through the slideshow, which was drawings, not pictures, I could think of nothing except "I don't care what the inside looks like, it's all bright blue and yellow squiggles, and if I'm curious about the outside I can go look in a mirror."
That was at public school, too. I transferred to private christian school in 6th grade and received even less sex ed from there. This was the area where mentioning the genitals could get you sent to the guidance counselor (who was an extremely fruity, creepy fellow who wore bright pink pants, whole 'nother can of beans).