L. Bennett Graham, Defamation of Religions: The End of Pluralism?, 23 Emory Int'l L. Rev. 69 (2009).
This article, written by a staff member of the Becket Fund for Religious Liberty, offers a nice summary of the history of the "defamation of religion" resolutions that have appeared in the United Nations over the past decade.
According to the article, the idea started in 1999 when Pakistan introduced a resolution against "defamation of Islam." The resolution was broadened to include all religions, and passed without difficulty in the U.N. Commission on Human Rights. Later attempts to pass the resolution, in both the Commission and the General Assembly, were successful but with diminishing support. In the past few years, the number of "no" and "abstain" votes have outnumbered the "yes" votes.
The author clearly opposes the "defamation of religion" resolution, arguing primarily that the legal concept of "defamation" is unworkable if applied to abstract concepts like ideas or religions, because truth is a defense to a charge of defamation, and what democracy-minded judge wants the burden of deciding if religious ideas are true or false? There's also an argument that the U.N. has illogically conflated racial discrimination and religious discrimination, but this point isn't sufficiently fleshed out.
On the whole, the article isn't a deep analysis of the problems with "defamation of religion", but it does provide a nice overview of how the resolutions evolved at the U.N.