From Tyler Cowen, writing at MarginalRevolution about a separate post by Scott Sumner:

…a lot of the debate about taxation is more about showing the wealthy that they need to lose (or win, on the other side of the debate) a few political battles than it is about actual canons of efficiency or, for that matter, even well-specified theories of egalitarian justice. For instance, I find that few proponents of a higher inheritance tax realize it will increase current consumption inequality by encouraging the wealthy to consume more rather than paying the tax. Nor do they seem to care, once this is pointed out.