I have been doing some extensive reading on just this subject recently. I will probably get around to writing a thorough thread at some point, and boring you all to death... In the meantime, some overviews.
All non-corrupt governments censor certain types of expression. Perjury laws, bans on certain forms of pornography, and conspiracy laws are all examples of censorship. Excluding them from the definition of expression would have a chilling effect on other forms of valid expression, and so they must be dealt with on an individual basis. There are extensive bodies of legislation and jurisprudence on what constitutes reasonable limits on freedom of expression in free and democratic societies. Democratic societies do not have absolute rights, because absolute rights can be used in ways which are not conducive to the principles on which free and democratic societies are based upon.
In that light, non-corrupt governments have a responsibility to censor certain websites, but only in a way that is demonstrably justified in a free and democratic society. So, in general, yes, but a general website, no. Furthermore, independent systems of accountability are necessary as well to demonstrate the justification.