They argue that we don't have to worry about the Laffer Curve because high tax rates don't discourage taxable income.
They argue that we don't have to worry about double taxation because high tax rates don't discourage saving and investment.
They argue that we don't need fundamental tax reform because tax burdens don't have much impact on economic performance.
They argue that we don't have to worry about punitive marginal tax rates because such policies don't discourage work.
It's unclear, though, whether they really believe their own rhetoric.
After all, if taxes don't affect economic behavior, then why are folks on the left so terrified of tax havens? Why are they so opposed to tax competition?
And why are they so anxious to defend loopholes such as the deduction for state and local taxes?