This is by the director of the Adam Smith Institute, Eamonn Butler, and ran in the Wall Street Journal Europe under the headline "The Moral Case Against Soaking the Rich":
Evidence from across the world is clear: take more than a third of people's earnings, and you unleash a silent tax revolt. Citizens rearrange their affairs in order to avoid the tax, or work less and retire early, or move their money or their businesses or even themselves abroad. They may even evade the tax by lying about their wealth and income, or taking payments in cash. And people abroad will be discouraged from investing in your country.
It is no wonder that low-tax countries grow much faster than high-tax ones. This growth-rate disparity is not just an economic problem, but a moral one. High taxes choke off business, employment and growth opportunities that would benefit the whole population. It cannot be "fair" to make everyone worse off....
Nor is it moral that high taxes crowd out private giving. People in the United States, whose government takes 27% of the national income, give more than twice as much to philanthropic causes as those in the U.K., which takes 40%.
I think when one adds in state and local taxes or spending the American government share of GDP one gets to well above 27%. But the points are well taken.