Kill Your TV, again
I think that our moral intuitions are strongly influenced by our sense of what is "normal" in society. (Types partial to High-falutin' language use the term "normative.")
Sadly, that sense is influenced by both those we know, and by popular media. The "peer pressure" aspect of the former has been a part of the human community forever. The influence of the latter has supplanted the oral and ecclesiastic traditions which once communicated cultural content from each generation to the next.
So whereas kids once absorbed the fireside tales of their parents -- who'd seen the difficulties arising from indiscriminate sex and would therefore not glorify it in their storytelling -- now they learn what life is like from popular media.
(They learn that good clergymen are always full of doubt, and clergymen who don't doubt their faith are either molesters or dangerous fanatics. They learn that generals are jingoistic madmen. They learn that newspaper reporters are heroes when they reveal government secrets, which are always dark and nefarious. They learn that Middle-Eastern Muslims never hold any beliefs incompatible with free societies, but that skinheads are the most significant source of terrorism in the world. They learn that businessmen are greedy crooks who'll murder for profit. They learn that Republicans hate the poor and Democrats love the poor. They learn that God doesn't exist and scientists are champions of truth and freedom. They learn that supernatural power, if it exists, exists in pagan magic, not in Christian prayer. They learn that religious people are bigots, wives are always smarter than husbands, teenagers see life more clearly than adults, and homosexuals are more emotionally healthy than heterosexuals. They learn that everyone is extremely thin and attractive, that an unattractive girl is actually just a stunner wearing glasses who'll inevitably become prom-queen after she gets a makeover from a knowing friend, that the prime nerd in high-school will turn out to look like a cover model for Men's Health once he's had a similar makeover, especially once he's undergone a training regimen made quick and painless by an inspiring rock music soundtrack, and that everyone has money to buy new stuff and to live in spacious surroundings, though one rarely sees them having to actually work.)
Anyway, the point is that when all that crap has already influenced one's sense of the normal, only a strong exposure to obviously contrary evidence in the real world will be able to make one's sense of the normal more realistic.
So, it would be one thing if kids absorbed all those skewed lessons from the modern world's equivalent of an oral tradition, only to find, when they talk to their friends, that not one of them has had premarital sex.
It's quite another thing when, after forty years of being saturated with those skewed lessons, kids have pretty much fallen into line with them, so that there is little contradictory evidence to be found anywhere.
Hence, it matters if all our friends are boinking like bunnies. It doesn't override our sense of free will, but it dulls our moral intuitions about what actually matters. It helps makes the grass seem greener on the other side of the moral code. And it reinforces the popular media's claim to be a trustworthy worldview.
Now, one can't kill one's friends for being a bad influence.
One can, however, kill one's television.
Said it before; now I'm saying it again: Netflix. And/or Tivo. By means of technology, be selective, so that all the media-absorbtion of those in your household is heavily edited for content. Stock your Tivo with reruns from the 50's, 60's, 70's, and so on: Why not?
The sole reason "why not" is of course that one doesn't wish one's kids to become the moral equivalent of "The Boy In The Bubble" who had no immune system and could be killed by the common cold.
Therefore, one should consciously introduce the bad stuff. Get some swearing in there, some teen sex, some pedophile priests, some sadistic soldiers, some religious types who overdo it.
But keep it in proportion. This will have the salutary effect of (a.) creating a better sense of proportion in a kid's sense of normalcy, and (b.) constitute sufficient exposure to lies and temptations to thereby activate the moral immune system.
All this, of course, falls under the category of "coming up with a theory of what might help, implementing it, and praying for the best." Which, from what I see, is a large percentage of the experince of being a parent.