C.S. Lewis and Censorship

The following quotation makes me wonder why many "conservative" Christians love Lewis but enforce strict censorship on their children.

"There were books in the study, books in the drawing room, books in the cloakroom, books (two deep) in the great bookcase on the landing, books in a bedroom, books piled as high as my shoulder in the cistern attic, books of all kinds books readable and unreadable, books suitable for a child and books most emphatically not. Nothing was forbidden me." Autobiography: Surprised by Joy  C. S. Lewis