Rednal
There... seems to be something of a trend of "Sexual = Sinful". I'm not entirely sure why. Among other things, humans are designed to reproduce a specific way, so clearly, sex itself cannot be bad. Otherwise God would have created a situation demanding people sin in order to perpetuate the species. Which, of course, makes no sense at all. The whole point of sin is that people choose to do it, and while they (usually) choose to have sex... choices themselves aren't inherently sinful, and that's an awfully silly thing to look down upon. "I need you to reproduce, but I will find you guilty for doing what I need done"...? Again, ridiculous.

In fairness, though, a lot of this stuff is sort of social traditions that have come up over time. For example, at the moment, we view polygamy as bad... but we have records of Prophets with multiple wives. And kings who talked with prophets but were never (on record) called out on it by them. Hmm. Yet many Christians are fixated very intently on "One Man, One Woman". But like I said, social tradition, where views change over time and are influenced by many factors.

Also in fairness, not everybody seriously questions their beliefs to figure out why they think the way they do, which does sort of make it their fault...
I'm actually somewhat puzzled at something myself, lately. I'm trying to find something that actually states premarital/nonmarital sex is bad without being roundabout. I know there's some old levitican junk about how if a woman gets pregnant, she's supposed to be married off to the father, but I'm looking for New Testament.

There's the frequently misused "Adultery" which is, in reality, cheating; then there's "Sexual Immorality" which is really hard to pin down on what it actually means because it's so vague. You'd think there would be some talk of promiscuity, but I imagine it was just so rare for men to be unmarried back then that it was hardly a vocally addressed thing. It SOUNDS like it would be considered a sin, but I'm just having the hardest time finding some objective evidence behind making that assumption.