Update (2013 Feb 4): Noah Smith has an awesome response to the attack on Prof. Krugman, too.
This seems to me to be a basic divide between liberals and conservatives (or, at least, the conservatives who dominate the right at the moment). Liberals see the world as data-rich, model-complex, and infinitely varied. Conservatives want the world to be simple, precept-driven, and authority-based. They want bumper-sticker policies.
Each side accuses the other, with some justice, of hubris. Conservatives say that liberals are so arrogant that they think they can change human nature and upturn thousands of years of received wisdom. But conservatives suffer from their own arrogance: The delusion that the world is static and simple; that human nature can be comprehended in a not only finite but small set of precepts; that you can reason from rules-of-thumb that work on small scales to vast interlocking systems; that what is true is always obvious — the delusion that no one, in fact, is smarter than a fifth grader.
After all, that’s the origin of the wildly misleading “If a family has to balance its budget every month, why doesn’t the government?” (We’ll leave aside the fact that families in fact do incur debt, and have good reasons to do so.) The national economy is not a household budget, of course, and to argue that it should be run the same way is silly at best and perhaps insane. Things that work at the household level are unlikely to extrapolate to an intertwined world economy. Even if there are broad principles to be deduced, their application will necessarily be complex.
To get back to my main point: Although conservatism used to have intellectual giants who correctly confronted liberal theorists with hard questions, those days are apparently over. (Witness the coup within the Cato Institute and the general decline of the Heritage Foundation; witness the concurrent meteoric ascent of Rush Limbaugh, Sarah Palin, Rick Santorum, Herman Cain…) Conservatives no longer want sound answers to important questions; they want comforting answers to simplistic questions. They have abandoned the “reality-based community” and forsaken the “evidence-based world”.
This is a slightly more genteel version of the virulent anti-intellectualism that defines the conservative movement of the day. To the right, when you hear data that confounds your expectations or worse, your desires, the instinct is to reject not only the data but the idea of data. That’s how you get climate deniers, birthers, poll “unskewers” — a vast sweep of people whose commitment is to the idea that numbers are meaningless. These are not isolated outbreaks of irrationality that mar the otherwise-pristine right. They are surface symptoms of an interlinked pathology, and “ask a child’s questions” is just another expression of it. You can’t spend forty years reflexively demonizing “intellectuals and elites” without driving them from your party, either literally or by self-selection.
Why is the “right” way to debate Paul Krugman to repeatedly ask questions a child would ask? Because their philosophy isn’t fit for grown-ups. It takes maturity to appreciate nuance, to rely on data (even when it says things you don’t like), to reason deeply. Modern conservatism seems to be inherently infantilizing (which is actually funny, considering their knee-jerk abhorrence of the “nanny state”): Grab with both hands, define “fair” as “what benefits me”, put yourself at the center of the world; rely on totems; fear the monsters under the bed.
The world is more complex than that. The principles (and intellect) of a five-year-old are not equal to the challenge of understanding it. There is a difference between being childlike and being childish — modern conservatism has dived deeply into the latter.