Both Dan Kleinman and Ginny Maziarka frequently attempt to justify the acceptability of censorship in libraries by quoting from the Supreme Court ruling from the 2003 case United States v. American Library Association.
I've been meaning to write a post showing the fallacy of relying on this decision to support their cause. The decision is vary narrowly focused (as all Supreme Court rulings are) on the constitutionality of Congress requiring public schools and libraries receiving E-Rate discounts to install web filtering software as a condition of receiving federal funding.
Yes, Justice Kennedy's separate but concurring opinion states "The interest in protecting young library users from material inappropriate for minors is legitimate, and even compelling, as all Members of the Court appear to agree." But that is just a comment, and not part of the legal issue in question. Whether there is an interest in protecting kids from Internet porn wasn't the issue; the issue was whether Congress could force filters as a condition of funding.
Each statement within a ruling is not precedent; this statement is not precedent and does not have the force of law.
For more on this, see today's post on Censorship-Free Libraries. Thankfully s/he took the time for a more lengthy discussion on the inappropriate reliance on this ruling by Ginny & Co.
UPDATE: Censorship-Free Libraries has more superb analysis of the (non)applicability of US v. ALA to the West Bend library controversy here.