Classic liberal approach: appeal to the pride and arrogance of young people by telling them that if they believe what liberals say then they are smarter than their parents.
I know it's the Onion, but topical nonethelless.
Surely it is easier to indoctrinate people to believe faleshoods if one starts from the cradle. They can be told the articles of faith, from an age where they can not understand, and are not equipped to challenge them rationally. Then, when they are older, they will defend their faith against rational challenges, because they "know" the truth. It is a settled matter.
Trying to indoctrinate an older person is much more difficult. When presented with an article of faith, the older person is equipped to analyse it objectively, and compare it to what he knows to be true. If you tell an mature person it is warm, he is liable to look out the window and see three feet of snow on the ground and conclude that you are incorrect. One has to appeal to the person's trust in higher authority. If those authorities are shown to be unreliable, convincing the mature mind is almost impossible.
Look at the teaching of religious faith for an example of this phenomenon. As the Jesuits say, "Give me a child until the age of eight, and I will give you the man". If the articles of faith can be established in the mind of the child from the earliest age, he will maintain that faith for the rest of his life. This is why parents who wish to raise wise and God-fearing children should begin religious instruction on the first Sunday after birth, and maintain it until the child leaves home.
The alternative is to try to convince the rational child of ten or fifteen years, which is almost impossible. By that time the ship has sailed, and you are in for much rougher sledding. It is still worth doing, of course. It is just much more difficult.
I say this as a person who is whole-heartedly in favor of indoctrinating children into religious faith, who wishes more parents would be smarter about it. Because if the parents don't indoctrinate their children, the State will get first crack at them when they enter preschool, and fill their heads with whatever leftist or environmental claptrap is the style of the time. Somebody is going to tell your child what to believe. Do you want it to be you, or Bill Nye, "Science Guy"?