1. I do not mean to suggest that I have inherent credibility based on credentials or somesuch.
2. By "classroom" I mean to suggest decorum. By "my classroom" I mean to suggest that I have a claim to jurisdiction. The Internet as a whole is a free-for-all, but this blog is not.
3. I have a long history of wanting to see decorum in the comments section. I believe that insults and personal attacks detract from the comments section. See Gresham's Law of Comments.
4. Historically, I have been more willing to tolerate commenters insulting me than I have been willing to tolerate commenters who insult one another. But I have come around to the view that those who insult me also damage the comments section.
5. Wit and friendly sarcasm are fine. I do not have a precise definition of what counts as acceptable and what does not. You shouldn't be spending time figuring out where the edge of the line might be. You should spend time figuring out how to express yourself in a way that is convincing rather than demeaning to others.
6. In some ways, my opinion about what counts as a good argument is more important to me than any substantive position that might be under discussion. I am willing to change my mind on issues, such as Global Warming or the FairTax. But I have laid out some clear markers about what sorts of arguments would change my mind. I think that is a better way to approach a debate than to throw insults back and forth.