The double tax oversight. The Berkshire Hathaway magnate makes much of the fact that he paid only 17.4% of his income in taxes, which he considers unfair when salaried workers often pay more. But Mr. Buffett makes most of his income from his investments, in particular from dividends and capital gains that are taxed at a rate of 15%.

What he doesn't say is that much of his income was already taxed once as corporate income, which is assessed at a 35% rate (less deductions). The 15% levy on capital gains and dividends to individuals is thus a double tax that takes the overall tax rate on that corporate income closer to 45%.

This onerous tax on capital is a U.S. competitive disadvantage in the global economy, which is why Congress agreed in 2003 to cut the rates on dividends and capital gains. Even as the rest of the world is cutting tax rates on corporate income, Mr. Buffett wants to raise U.S. rates in a way that would make America less attractive for investment. Under a sensible tax reform, the feds would impose either a corporate tax or a dividend and capital gains tax, but not both.