Argument: Progressive taxes adjust for random factors in wealth
"In support of progressive taxation". The visible hand in economics. 12 Nov. 2008 - there are reasons why society may want a progressive tax system, and when it would dominate other tax systems: [...]Society may believe that it is fair for those who are “endowed with luck” to pay a greater amount of tax - even proportionally so (often diminishing marginal utility is used for this - but that is a “cardinal” sin (ignore my economics pun)),
Robert J. Shapiro. "Flat Wrong: New Tax Schemes Can't Top Old Progressive Truths". Washington Post. 24 Mar. 1996 - The positive case for progressivity as the better measure of tax fairness emerges more clearly from the underlying issue of income differences. In theory, flat-taxers are right to criticize a tax system that would penalize people for differences in income that reflect only how hard they choose to work. In real life, income differences reflect much more than effort, if only because people don't start in the same place. At the least, people are born with different talents and grow up in families, neighborhoods and cultures with different resources to prepare them for market competition. Luck usually plays a part too. Moreover, the more free markets are, the larger the rewards people can secure by leveraging their talents, resources and good fortune – and America's markets are generally more free than those in other advanced countries.