I felt as if I had been asked to justify why water had to be wet. Here was someone who depended for his living on the right to free speech, who wrote as an adult for other adults, who was advocating the false assumption that lies at the core of the censorious impulse: Children need to be protected from vulgarity and obscenity.

At the heart of that argument is the belief that society should be remade for everyone, not just children. Basically, my friend was arguing that all adult discourse should be rendered suitable for kids, that entertainment or writing specifically intended for adults is somehow dangerous and that, as journalists, we should all be required to adhere to a phony "family newspaper" standard.

He didn't come out and say that, of course. He fell back on the protection-of-innocence arguments that censors have used for years and that courts have upheld. There's an understandable impulse behind the desire to protect children, an awareness of their physical fragility, a wish for them to be able to enjoy their childhood and a frustrating sense that out in the world dangers await them that we are powerless to stop. But too often we have lost the ability to distinguish between what's inappropriate for kids and what is actually harmful to them. And, acting on fear and suspicion and assumption, we have, with the best of intentions, created situations that are potentially more harmful to kids and teens than what we want to protect them from.

The tradition of censorship in the name of the little ones is the subject of Marjorie Heins' new book, "Not in Front of the Children: 'Indecency,' Censorship, and the Innocence of Youth." Heins, the director of the Free Expression Policy Project at the National Coalition Against Censorship, has essentially written a précis of various legal rulings that have cited the protection of youth as justification for limiting free speech. Heins is blessedly clear on the legal ramifications of the obscenity prosecutions she considers. As a lawyer she's adept at pointing out the contradictions, false premises and just plain unconstitutionality of those decisions.

But Heins' book is essentially a long legal brief, and that narrow focus is disappointing. Put it this way: No one is likely to attempt to write a history of how in 20th century America free speech was denied and narrowed in the name of decency and protecting minors without consulting this book. But we are still awaiting the great piece of social criticism about modern society's fetishistic construction of childhood as a time of asexual innocence.

By any reasonable standard, that fantasy has to be counted among our most destructive and costly delusions. It's a poisoned tree that has borne the fruits of censorship; of teenage lives stunted or ended by denying minors access to birth control, abortion and sexual information; and of adult lives destroyed by the urban legend of ritual cult child abuse (best dealt with in the 1995 book "Satan's Silence" by Debbie Nathan and Michael Snedeker) or by the junk science of repressed memory syndrome (the subject of Frederick Crews' pitiless and incendiary "The Memory Wars").

Maya Angelou reads from "The Heart of a Woman"