Knaves or Fools? Why Choose?

Matthew Yglesias, I think, gets one wrong. He says that Steve Spuriell is not a knave but merely a fool:

Matthew Yglesias: Stephen Spuriell on Student Loans: One major analytic error I think liberals tend to make is vastly overstating the level of dishonesty among conservative pundits, analysts, advocates, etc.... [T:]he overwhelming majority of smart people with conservative political opinions are working as businessmen.... So you’re left with a kind of denuded population in terms of...