In my recent podcast with Robin Hanson , he mentioned a Paul Graham essay, "Lies We Tell Kids."  I found it to be a fascinating read and recommend Graham’s essays.  At Robin’s blog, Overcoming Bias, he quotes Graham’s argument  for why we lie to our kids about the dangers of the world:
is also open-mindedness. We want kids to be innocent so they can
continue to learn. Paradoxical as it sounds, there are some kinds of
knowledge that get in the way of other kinds of knowledge. If you’re
going to learn that the world is a brutal place full of people trying
to take advantage of one another, you’re better off learning it last.
Otherwise you won’t bother learning much more.
Very smart adults often seem unusually innocent, and I don’t think
this is a coincidence. I think they’ve deliberately avoided learning
about certain things. Certainly I do. I used to think I wanted to know
everything. Now I know I don’t.
I don’t know if there’s any merit to this argument. Robin writes:
This has some
intuitive appeal, but it is puzzling – why exactly would learning that
the world is a brutal place make one less interesting in learning more
about that world? Wouldn’t learning help one to avoid brutality?
Maybe. But knowing about brutality has other effects. I think Robin and Graham miss the real reason we lie to our kids about the brutality of the world, and about sex, and lots of other things. We believe, perhaps correctly or incorrectly, that experiencing brutality at an early age is scarring not liberating. It diminishes a person as an adult. So a child who watches R-rated films filled with sex and violence at eight years old is more worldly and knowledgeable than a sheltered child, but also more damaged, a child who upon adulthood is less able to cope with violence and sex. This could be a delusion we have about raising children and the real reason we protect them is to keep them cute or malleable or something else. And maybe the damaging effects of learning about brutality is what Graham is getting at when he talks about open-mindedness.
I remember a fellow 7th-grader, L., who knew much more than the rest of us about the mechanics of the birds and the bees and who patiently talked about those mechanics in a totally matter-of-fact manner to anyone who was interested. Most of us tried to appear as knowledgeable but I suspect our parents’ more guarded treatment of the topic made us see sex as some mysterious and powerful force. For L, it appeared to be akin to learning about how to eat wisely or dress appropriately. Did L’s parents do him a service or a disservice by treating sex so openly? I don’t know. It’s hard to know. Most of us follow the taboos and conventions around us. They have a long tradition behind them. That is some justification but not every taboo and tradition is healthy. Read the Graham essay. As always, he has much to say that is very thought-provoking.