Mitt Romney, and others like him, are weakening "the bonds that hold a society together":
Mitt Romney’s Fair Share, by Joseph Stiglitz, Commentary, Project Syndicate: Mitt Romney’s income taxes have become a major issue... Is this just petty politics, or does it really matter? In fact, it does matter... Economies in which government provides ... public goods perform far better than those in which it does not. But public goods must be paid for, and ... those at the top of the income distribution who pay 15% ... clearly are not paying their fair share. ...
Democracies rely on a spirit of trust and cooperation in paying taxes. If every individual devoted as much energy and resources as the rich do to avoiding their fair share of taxes, the tax system either would collapse, or would have to be replaced by a far more intrusive and coercive scheme. Both alternatives are unacceptable.
More broadly, a market economy could not work if every contract had to be enforced through legal action. But trust and cooperation can survive only if there is a belief that the system is fair. ... Yet, increasingly, Americans are coming to believe that their economic system is unfair; and the tax system is emblematic of that sense of injustice. ...
Romney may not be a tax evader; only a thorough investigation by the US Internal Revenue Service could reach that conclusion. But, given that the top US marginal income-tax rate is 35%, he certainly is a tax avoider on a grand scale. And, of course, the problem is not just Romney; writ large, his level of tax avoidance makes it difficult to finance the public goods without which a modern economy cannot flourish.
But, even more important, tax avoidance on Romney’s scale undermines belief in the system’s fundamental fairness, and thus weakens the bonds that hold a society together.
On the unfairness, beyond taxes Stiglitz also notes that:
...much of the money that accrues to those at the top is what economists call rents, which arise not from increasing the size of the economic pie, but from grabbing a larger slice of the existing pie. Those at the top include a disproportionate number of monopolists who increase their income by ... anti-competitive practices; CEOs who exploit deficiencies in corporate-governance laws to grab a larger share of corporate revenues for themselves (leaving less for workers); and bankers who have engaged in predatory lending and abusive credit-card practices (often targeting poor and middle-class households). It is perhaps no accident that rent-seeking and inequality have increased as top tax rates have fallen, regulations have been eviscerated, and enforcement of existing rules has been weakened: the opportunity and returns from rent-seeking have increased.
To the extent that this is true, those at the top are receiving income they didn't earn through their contributions to GDP. It is the result of rent-seeking -- they didn't "build that" -- and clawing back those gains through taxes is not unfair, and it does not distort economic activity. Instead it reverses existing distortions that send income to the top of the income distribution instead of to the working class as a reward for their increased productivity.