The non-religious demographic in the United States -- that is, people who run the gamut from atheists to agnostics to the simply non-religious -- is growing. It has doubled in the last 20 years, and the current rate of growth is stable. We're at 15% of the American population right now, and it's projected that we'll be something like 25% by 2030. I tend to think that this says a lot about the indoctrination of children into their parents' religion.
From my studies of language, I know that a child's brain is much more easily malleable than an adult's. Basically, they're wired to accept what they get when they're very young, and that capacity for learning diminishes gradually as they get older. I think parents realize that they play a huge role in how their children grow up. I don't think they quite suspect how difficult it is for them to change their minds when they're older. Therefore my argument here will posit that it is ignorance, and not malice, that causes parents to rob their children of choice.
59% of people who identified themselves as non-religious at the age of 12 have remained so. 88% of people who identified as religious at 12 have remained religious. At first glance, that may appear to be a strike against the ideological attraction of non-religion, but there are other facts to consider. Individual religious sects only retain 59% of their members. That means that, on average, among religions, 41% of people will leave the group they started in, including 12% who drop religion altogether. Also bear in mind that not every non-religious person, including parents, is particularly conscientious about it. Of the non-religious, only 10% consider themselves atheists, so the remaining 90% will be generally less opinionated, and likely won't have strong input one way or the other regardless of which direction their children go. Add to that the fact that religions, especially the ones practiced in this country, tend to have strong theological or at least social sanctions attached to apostasy, and it's easy to understand the difference in retention rates.
Consider the forces at work here. For a child raised religious, it is necessary to overcome first the worldview that's been driving your understanding of the world since childhood, then the fear of cosmic punishment for apostasy, then the fear of damaging relationships with family and some friends. Pulling the individual towards non-religion is only rational persuasive force, which may include criticism of particular scripture and reasoning based on the plurality of mutually exclusive religious belief systems. The sum of these forces causes about 11% of the total population to stop being religious. Let's look at the flip side. For a child raised non-religious, he must first see value in believing a particular religious worldview, then become convinced that whatever he's learned about science that contradicts the chosen religion (which varies based on the particular worldview to be assumed) is wrong somehow, then overcome whatever misgivings his family might have (which will tend to be scant if present at all in the case of an agnostic family, like most in the non-religious group). Given all that -- including much weaker familial repercussions for becoming religious than vice versa -- only 4% of Americans become religious who started as non-religious.
I'll put it here plainly: losing religion has far stronger social barriers associated with it than gaining religion, yet more than twice as many people lose religion (11%) as gain religion (4%). To say nothing of truth value, which I'm sure I'll address later, that means that the rhetorical force of non-religion must be far stronger than the rhetorical force of religion. Rational adults, when freed from the fear of social sanctions, leave religion more often than they seek it.
It's not difficult to see, given that, that there are many people who would have left their religion if it weren't for the combination of social sanctions and the fact that they were wired from a very young age to accept their religion as fact. This is why the indoctrination of children into their parents' religion should be seen as an abuse of their undeveloped critical faculties. But again, it's hard for me to fault individual parents. The meme of religion includes, as part of its program, an instruction to share it with your children: that's how it keeps itself going. It's what I call "meme insurance". The parents are no more at fault for that than your computer's operating system is for being vulnerable to any particular virus. Caveat, though: whether religion on the whole is bad is a topic for another discussion. What I'm asserting is that it's abusive for parents to favor one religious worldview over any other in their child's upbringing, because that robs many if not most children of the choice to change their minds later on in life. If you disagree on the grounds that your particular religion is more correct than all the rest, I suggest you find someone who would say the same thing for a different religion, talk it out, and please be informed by the fact that neither of you could convince the other.
You might retort, however, that it's no better to raise children as non-religious, because that's just another worldview, and doing so prevents them from changing their minds later in life. Here I must take care to define terms: when I say "religious worldview" or "religion", I mean a worldview that is explicitly supernatural. While it could be said that Humanism, Confucianism, and some manifestations of Buddhism have nothing really supernatural about them, they are still sometimes classified as religions; for my purposes in this post, those are merely philosophies, because it's useful for me to use "religion" as shorthand for "supernatural religion". Right. So, the core of my argument here is that a religion is (or contains) a set of propositions about the world that can be neither proved nor disproved. Religion is based not on evidence from our experience in the world but on a set of fables of dubious origin; this is why the concept of faith is so important, as it acts as more meme insurance.
As a set of extraordinary propositions, a religious worldview has the burden of providing the extraordinary evidence to support it. It is the right of adults to believe or disbelieve unsupported extraordinary propositions at their leisure. We know lots of ordinary things about the world, like the characteristics and behaviors of animals and plants around us; nobody questions whether we should teach these things to children. We also have a pretty good idea of some extraordinary things about the world, which would be useful for parents to know when their precocious toddlers begin an infinite regress of "why" questions; for these things, we have extraordinary evidence. A great deal of scientific inquiry has gone into the workings of weather patterns, the history of life on earth, and the movements of the planets. We have sufficient piles of evidence that it is responsible to teach these things to children.
Every religion has a set of holy writings and a number of personal revelations to back it up; yes, all of them, so it's impossible to say which revelations are the correct ones. It's easy to understand how they all could be false and still have arisen as they did in the light of science; in order to understand how all the science turned out the way it did in the light of a particular religion, however, you must assert a degree and quality of divine meddling that has to imply deliberate mischief. I'll grant, of course, that not all religious worldviews conflict so strongly with science as the young-Earth creationism view; if the scripture nevertheless states a recent creation which it intends as metaphor, then the mischief lies in the fact that its status as literal truth or figurative metaphor is in no way clear from the text alone. In any case, the evidence for one religious view is strongly enough equivocated by other religious views that we cannot say which is best on a rational basis; therefore, to mold a child's mind to believe that your particular religion is more correct than anybody else's is, to put it mildly, an affront to rationality.
My argument that raising children without religion is better than choosing a particular religion for them is based on the premise that learning scientifically established facts about the natural world will not be harmful to them in the future. A true understanding of science may bias children against some religious beliefs if they encounter them later in life. If that's the case, then it's incumbent upon the religions to adapt to the persistent flood of scientific evidence. If you deny that, then you posit that noncritical religious thought is somehow superior to critical scientific thought. My simple retort to that is to ask, if science doesn't have a lot going for it, how do you think they built the machine that's allowing you to read this? And if science works far more often than it fails, on what basis do you suppose that it's wrong in the case of your religion, with which, I remind you, most of the world disagrees?
So, to recap my points, not necessarily in the order I presented them above. 1. What you teach your kids is hard to undo later in life. 2. More Americans conclude, when liberated from their childhood belief structure, that religion is wrong than that it's right. 3. Many if not most people are prevented from choosing their worldview by indoctrination by their parents. 4. No religion has more positive evidence for its truth than any other. 5. Scientific propositions have positive evidence for their truth. 6. Therefore the only moral choice is to teach children only evidence-based truth, holding off the subjective and equivocal philosophies until they're old enough to choose for themselves.