Suppose someone sits down where you are sitting right now and announces to me that he is Napoleon Bonaparte. The last thing I want to do with him is to get involved in a technical discussion of cavalry tactics at the Battle of Austerlitz. If I do that, I’m getting tacitly drawn into the game that he is Napoleon Bonaparte.
-- Robert Solow (attributed)
Remember this, the next time some wingnut starts whining about "ad hominem!!!1!" and "Alinsky!!!1!" and "your not engaging on the merits!!!1!" (Yeah, that's how they usually spell it.)
(h/t: Matt Yglesias)