How do we convert people having seemingly no comprehension of sexual morality? It is like getting through a 10 feet wide stone wall. They have been given a counter-morality. They have been told that it is evil to believe in sexual morality. Of course, surely on some level they know this is wrong. On some level, surely they know it has become an issue of popularity. Are they simply pretending not to understand? Are they just unwilling to go against the currents? Are they really this confused?
C. S. Lewis said somewhere that you can't begin with fornication. For one thing, the sex drive is not contrary to nature or the natural law. And for those acts which are - well, we may know in our hearts that promiscuous and sterile sex, pornography or perversion is wrong, but now that society hails such sins as positive things, as good things, as commendable things, there's little we can do.
It seems to me that the renunciations asked for by a love for Jesus Christ make no sense on their own. Access to sexual adventures has perhaps never been so easy, at least since the decline of ancient Rome. To turn from such things seems utterly foolish and self-defeating to most normal people, and to avoid easy sex only makes sense in the context of a relationship with Christ.
Thus I agree with Lewis. You can't start with the evils of fornication and the benefits of chastity. That would be like preaching to a homeless drug addict about the joys of working a 9 to 5 job in a cubicle. Such a sacrifice has its rewards, and is a much better thing that abandonment to drugs and destitution, but it's certainly not the carrot on the stick. Now, I'm not comparing chastity to a life of drudgery; on the contrary, it is a bold and glowing thing, intensifying love and bringing light and dignity to man and woman. But to a horny teen, chastity seems no different than a life of unremitting wage slavery. To them it seems like a 9 to 5 job in a cubicle. And it won't seem otherwise until life seems otherwise; and life won't seem otherwise until they begin to catch a glimpse of the pearl of great price, for which all other riches lose their luster.