Maybe I'm misreading the article, but Chomsky seems to be saying that no one should be a moral relativist; that moral relativism is a nonsensical stance; that professed moral relativists don't really believe what they say due to internal contradictions. And while I agree with him on this, his arguments (as summarized in the article) seem weak and handwavvy; I choose to view this as likely an effect of the summarization.
Is there a longer-form write-up of his arguments anywhere? This article was very short and switches terminology a couple times.