Lots of early and influential church doctrine and theory had some very “don’t fuck ever and you should feel bad for fucking” elements in it. The relation in Abrahamic faiths towards sex and sin is very much evident and a fundamental part of the doctrine. This has been interpreted again and again by theologians all across time but in general sex as a necessary evil has been a prominent feature. While for most of history this sort of thing wasn’t being preached at the local church, the printing press changed a lot.
Most theological debates around sex and sinfulness tend to go in circles because of fun translation things, but there were a variety of sects that taught that original sin was Adam and Eve having sex. This certainly has an influence on St. Augustine, who as a married man is in a bit of a weird spot with all this. His view is that sex requires lust to happen, and as such the sexual act perpetuates original sin. Sex as a physical act divorced from emotion itself isn’t a good act either. While the act of marriage makes it not a sin (because it isn’t lust if it’s your wife… mostly) it’s not considered good either, which makes me wonder a bit about the love life of St. Augustine and just how much he picked up from the Mancheans. Paul also has a major influence on all of this, basically says that even marriage itself is a distraction from the commitment to God and should be discouraged and everyone should be celibate. Sort of. Paul’s letters were likely fucked with quite a bit during their integration into biblical canon. Gotta love early church arguments where various bishops attempt to murder one another over the relationship between the trinity, and how the serpent moved before being cursed by god. While plenty of later theologians and philosophers would go into the nature of love and sexual love when it relates to the divine, you’re blind if you think that St. Augustine’s views haven’t had a massive influence in the development of Christian doctrine from an early stage, and in thus, the modern fundamentalist Protestant sects, who seek a version of the religion that was never really preached or practiced before the modern era.