Wright reminds us that the problem of the sexual revolution is not the gravity of the sins. Other sins are far worse. That is not the problem.
Wright does not say it here, but it is the fact that sexual sins and diseases are being actively promoted and enforced as higher goods that makes the sexual revolution such a deep and damaging problem - not the unique depravity of sexual activities out-with real marriage.
And he makes the point that the problem began fifty years ago; when people began to advocate, indeed glamorize, a life of respectful serial promiscuity as superior to to 'slavery/ tyranny of marriage.
...When divorce without blame or rancour began to be advocated as morally superior to the monotony of monogamy; when the most solemn promise-breaking (and ripping up without hesitation the most carefully regulated, pondered and multiply-witnessed of all legal contracts - i.e the marriage contract) - was seen as admirable if it 'made people happy', or enabled their 'growth' (or, in actual practice, when it was what either of the parties - usually the woman - said she wanted at that time).
Over just a few decades, secular marriage became so debased as to make it almost indefensible; and we live in a secular society. For anyone not religious, what was there to defend. A piece of paper that did not even have normal everyday contractual status - less than a mortgage, a hire-purchase agreement, or a cheque.
But the real problem of the incremental legal destruction of marriage is that it was driven by - and led to the increase of - open, explicit, aggressive, enforced moral inversion: imposing the worse as the better, the pathological as healthy, the sin as a virtue.
And arguing to justify evil is the worst evil - worse by far than actually doing evil (because Men are weak, and often cannot help but do evil in particular circumstances).
All men do evil, but only the most depraved argue - strategically, and over many years - that evil is good; good is evil.
Luckily, any evil can be repented at any time. Unluckily, there seems no perceptible sign that this is about to happen - indeed, quite the opposite.