Some Evangelicals believe that women should be submissive in every way, including during sex. For these Neanderthals, the missionary position is the proper, God-approved way to engage in sexual intercourse. No oral sex, no anal sex, no trying out the Kama Sutra, and most certainly no woman on top sexual intercourse. Why? Because when the woman is on top she is in a position of dominance and control. Can’t have that. Thus, to answer the question posed in the post title: it is indeed a sin to save a horse by riding a cowboy.