From Rule #3:
We expect you to behave as if you were a guest in someone's home. Vulgar language, insults, name-calling, and that sort of behavior is frowned on — especially in the subject line where visitors are likely to be shocked to read an invective. If you disagree with another's opinion, especially if the opinion was not expressed to you nor was it made about you, do not become insulting. Allow others the dignity to freely exchange opinions without flaming either of the participants in an exchange.