Intellectual Dishonesty by a Conservative Economist?

Here's a fun exchange talking about tax policy that I'm completely unqualified to evaluate, but I still have my opinions. I read blogs by both authors:

Harvard economist Greg Mankiw wrote this article in the New York Times: Is Government Spending Too Easy an Answer?

Then Nate Silver of FiveThirtyEight.com wrote this critque: Politics Done Right: Intellectual Dishonesty (Gasp!) from a Conservative Economist

Mankiw responded in The Importance of Being Exogenous.

And Silver responded in Is There a Serious Conservative Argument Against the Stimulus?.