Regardless of your views of the use of the "n-word" in Twain's classic work and the fact that it was a private business -- not the government -- who did the "censoring" (though various local governments have banned the book because of the language), it seems a bit strange that a person whose entire living is based on First Amendment protections of speech and press would see censorship as a good thing in general.
We have a response for Mr. Kristof:
