Advocates of the sexual revolution often point out that most mainstream sexual sins are not all that sinful in the larger scheme of things.
They are right.
Why, then, are sexual sins (those advocated by the sexual revolution) perhaps the largest underlying problem in the West, and sexual sins are primarily responsible for the catastrophic decline and (near-) death of Western Christianity?
Firstly, because sexual sins are so popular - unlike murder, many people want to do them (or, at least, be able to take the chance of doing them, if the opportunity arises).
But secondly - and far more importantly - because sexual sins are not repented.
Sexual sins are not repented in our culture, because people have come to deny that they are sins at all. You cannot repent a sin if or when you deny it is a sin.
From arguing, correctly, that these are not necessarily very big sins, people have concluded that sexual sins are not sins at all - therefore they do not need repenting.
Indeed, many self-identified Christians have begun (usually indirectly, sometimes explicitly) promoting sexual sins - as if they were virtues; for example they criticize or punish people who recognize that sexual sins are sins.
(This pattern is altogether typical of unrepented sin - it leads on to moral inversion.)
Repentance wipes us clean of sin - that is the gift of Christ's atonement. But failure to repent is what chains us to hell, because it entails a deliberate rejection of God's order.
It is not by committing some spectacular sin, but rather clinging to a 'minor' sin that is probably the main cause of (self-) damnation.
(CS Lewis portrays this convincingly in The Great Divorce - where souls in Hell are shown Heaven, and offered the chance to dwell there - but at the price of repenting their favourite, habitual, 'minor' sin; the sin around which they have organized their lives: Most choose to stick with their sin and stay in hell.)
We are safe from sin if we know and acknowledge sin; repent and repent again.
We may not reform our behaviour, we will very probably continue to be sinners of the same type to a greater or lesser extent; but sin cannot get a grip on us. Salvation is assured.
But unrepented sin - even one, no matter how relatively minor it may be - can, and often does, take hold and tighten its grip, until we are altogether pulled-down by it.