Sexuality is a basic part of humanity, and they're being told to repress it and feel guilty over its expression (it's tied in to sin, after all). Several things about religion are anti-human; the prevailing attitude in the Dark Ages was that the human body was inherently sinful, and we've still got concepts like original sin and "fallen" man popular even today. Hell, at one point in the history of Ireland, having sex consisted of man and woman, clothed, doing it only to conceive in a dark room, both full of shame.
Money should instead go to responsible sexuality, such as the use of contraceptives, family planning, and relationship education.
First, "Dark Ages" is a defunk term. You might as well call the United States "The Colonies" while you are at it.
Second, your anger should be more directed at Puritans (which were
post Middle Ages) than Catholics. This is not to say that the Catholic church taught sexual liberty, but sex in the Medieval period was not so repressed as is sometimes perceived. It is true that the Catholics did believe that sin is passed through sex, but it was not the act itself that was at fault sinful. Rather, much like apostolic succession, sin is being traced back to the original sin of Adam. If one knows where to look, sex was almost downright liberal in the Middle Ages.
Some puritans, on the other hand, tended to believe that nudity and sex were indeed inherently sinful and ought to be avoided at all costs. Indeed, some believed that exposing yourself to yourself was a sin. Curiously, most group that were that extreme died out fairly quickly. However, the American uneasiness with sex can be traced back primarily to Puritans (post Middle Ages), not Catholics (Middle Ages).
Of course then there were those crazy Anabaptists at Munster and various Gnostic sects who believed that private anything was sinful, and as such sexual partners were to be communal. Some such groups even believed that sex was worshipping god. Then there's the "Full Quiver" groups now-a-days... such individuals tend to be in need of a good smack upside the head.
Third, while repressing one's sex drive out of shame (a concept that we can find root of in Greek philosophy) is indeed antihumanistic, the concept that humans can't suppress their sexual drives is likewise so. To say that kids having sex is inevitable seems to be akin to saying that men are controlled by sex (see the Fuck Sexism thread).
