How the fuck can sex be a sin?

Firstly I deny there being such a thing as sin anyway so to draw a line and say "You may enjoy tasting food, looking at nature, listening to music but you MUST NOT enjoy sex, especially with yourself" is balmy.

This debate must have occurred on a thousand occasions so I have little to add here. In fact the debate must have gone on for generations and if it went on for generations, then, someone was fucking during that time.