I think that many people can agree that religious extremism is problematic. But my problem with religion or religious dogma goes beyond the obvious danger of its radicalized forms. I want to discuss the potentially dangerous consequences of indoctrinating children into a religion or superstitious belief system. Indoctrination is a form of behavioral conditioning. In the case of the major religions, this often takes the form of conditioning the child to believe in highly improbable or fantastic things, to believe these things unquestioningly, i.e. to take things on faith, and to cede matters of morality to an absolute and infallible authority, a god, whose preachments are given in a holy text which contradicts itself, but the contradictions are overlooked by the mind that has been conditioned to believe unquestioningly. This religious conditioning, usually under the guise of moral education, amounts to brainwashing. And it can permanently impair a person's judgment.
Young children are particularly vulnerable to indoctrination because they are at a critical stage in their cognitive development when ideas and habits become hard-wired. Children readily absorb information in the form of language, ideas, and the examples provided by their parents, teachers, and friends. Children are quick to learn new information, excel at mimicking, and are very apt to model the behavior of their parents. This is why parents must be especially careful with their children's education. Parents who teach their children to believe unquestioningly in religious doctrine, even when that doctrine contradicts reality, are committing a form of child abuse by conditioning their children to take things on faith rather than evidence, thus impairing their children's ability to think critically and make rational decisions, i.e. decisions that are well-reasoned, based upon evidence, and optimal for achieving a goal or solving a problem.
Parents have a responsibility to teach their children to think critically, not to discourage critical thinking. It is a matter of giving children the tools they need to distinguish fact from fiction, to decide whether what they are told really makes sense or is false propaganda, to stop for a moment and check that the road ahead is safe, to consider the consequences of their actions, and to engage in the kind of introspection that tests one's assumptions and facilitates understanding.