Two excellent Alternet articles cover a recent tome worth examining: Censoring Culture: Contemporary Threats to Free Expression edited by Robert Atkins and Svetlana Mintcheva.
On the justification for censorship:
"Of the many debates about censorship in recent memory, not one has opened with a public official saying, "Let's censor this." On the contrary, the standard initial talking point is "This is not censorship, we do not censor, "followed by: "We need to be sensitive to community standards"; "We need to protect children who might see this"; "We can't spend taxpayers' money to support work that might offend"; or "We don't consider this censorship at all, because you are free to exhibit your work elsewhere. "The censor's current disguises of choice are the moral imperatives of "protecting children"and of exercising "respect for religious and cultural beliefs and sensitivities" -- both, in themselves, laudable objectives, and for this reason, perfect disguises for other, less savory motives."
On the issue of self-censorship:
"A discussion of censorship that only takes into account attempts to repress existing works, however, misses all those works that never came to life: Perhaps, because this novel didn't seem sufficiently commercial, there was no chance of its being published or, perhaps, because that play might have offended somebody, the playwright censored himself at the outset and decided not to write it at all."
On the need for censorship in lieu of protecting children:
"... the problems most affecting children -- poverty, the state of public education, a lack of health care and, in too many cases, parental neglect -- have nothing to do with pedophiles. Hunting for them among middle-class mothers, banning drawn or photographed nudes in public exhibition spaces, or bleeping four-letter words from TV broadcasts is unlikely to solve any of these problems."