These folks MIGHT have misunderstood “the gospel of modern Christendom.”
What “modern Christendom” has presented as the gospel has ALWAYS been a mixed bag from the word go. From observation, I regard many (though not all) modern Mormon organizations as very badly confused Christians rather than as fundamentally apostate from Christ. They are a kind of meta-Protestant, but with a lot of garbage doctrine confusing the way.
At any rate, it looks like their attempted defense against sexual immorality is a lot of “don’ts.” The great secret of the ages is that the defense is not found nearly as much in don’ts as in do’s. DO present your body boldly to the Lord, complete with all its desires and passions, confused or otherwise. Pretending they aren’t there only results in pockets of sin that never get taken care of in this mortal coil. Sin is bad aim; it came to pass because of original sin devotion to the devil (through various means). It is forgivable and healable. God is the consummate straight shooter and will teach you how to shoot your arrows. But don’t hide them from God. That’s the worst thing you can do.
There went breakfast; and I've not even eaten it yet!