Greg Mankiw is not making a lot of sense

I used Greg Mankiw's textbooks in college and read his blog every day. But in this Washington Post forum Mankiw makes two arguments against Obama's progressive tax plans that I find pretty puzzling. They are:

CBO data show that the tax code, including all federal taxes, is already highly progressive.


President Obama's proposal to raise taxes at the top to further cut taxes at the bottom has one rationale: using the coercive power of the state to "spread the wealth around." [This] raises deep philosophical questions. If one citizen of a nation can lay claim to the wealth of his more productive neighbor, shouldn't poor nations have the right to lay claim to the resources of richer nations such as the United States?

Let's see what's wrong here:

Fans of David Hume and G.E. Moore will recognize that Mankiw's first argument falls face first into the naturalistic fallacy. Mankiw cannot get an 'ought' from an 'is.' A description of the current tax code has absolutely no implications -- zero, zip, zilch -- for how progressive the tax code should be. The fact that we already have a progressive tax code is not an argument against making the tax code more progressive.

As for Mankiw's second question -- well, I think the answer is pretty clear: No. Redistributive decisions within the United States have no necessarily implications for redistribution outside the United States. The reason has something to do with a thing called "democracy." I suspect Mankiw has heard of this because we live in one. Our constitutional democracy isn't a system in which some poor schmo can "lay claim" to his rich neighbor's garden hose. It's a system in which we make majoritarian decisions about issues of fairness and distribution and submit to be governed by them. One such majoritarian decision came around last November.