From this article in Touchstone: ". . . immerse your child in the worship of the Church and every other activity that can shape his imagination as Christian because he acts it out. The greatest prophylactic against cultural infection is not a shield but his love for something better and greater and more heroic."
Attempting to isolate our children from every evil influence leads eventually--or quickly--to panic. If they don't go to school, there are "school kids" at Sunday school and VBS. If we forbid Judy Blume we're left to figure out what to do with Ramona (and what about all that "obey" business in These Happy Golden Years?) We can choose our children's friends, or choose that they not have any, but we can't choose their cousins.
We can't just tell them, "That's trash. We don't read those books. Cartoons are for the masses. Parades are for Americans. The kid across the street is vulgar. Pudding cups are poison. Tryphosa dresses like a trollop, and does not nature itself teach us that Aristarchus needs a haircut?" I mean, sure, we tell them those things. But that's just to impress ourselves. Those statements provide children no nourishment. It is far more important to actively cultivate in them virtuous habits, good tastes, and noble interests.
A child who is fed primarily on contrarianism will become either rebellious or a hollow parody devoid of character. I'm inclined to think the latter is worse--the child who rebels to break out of an artificially insular world at least shows initiative and concern for substance. Isolationism is a losing battle anyway: even if they never leave our houses, children are born full of the world, naturally embracing trinkets and SnakPaks and jingles and sulking.
Beauty is truth, truth beauty, and that is what they need know on earth. Those who know and love and hunger for what is true are much harder to deceive. If our kids can't eat pudding cups--and they certainly can't--they are left ravenous and resentful if we stop at denying them. They must be given something much better. It will take a lot longer to make.