<p>I find the “fairness” argument to be quite weak.</p>
<p>Better reasons for a progressive tax:</p>
<ol>
<li><p>More revenue. The Laffer curve is widely regarded as false. Taxing the rich at a higher rate is the easiest way to pay for roads, fire departments, police, etc. A 10%-40% progressive tax will generate an insanely higher amount of revenue than a 25% flat tax.</p></li>
<li><p>Strong economy. Taxing the rich does reduce supply a little, but taxing the poor/middle class sharply reduces demand. A 10%-40% progressive tax, therefore, will have less of an economic impact than a 25% flat tax, because a 15% increase on the poor will wipe out some people’s disposable income. A 15% increase in the upper bracket could hurt investment, but it wouldn’t wipe it out, and consumption would be unaffected.</p></li>
<li><p>Less BS. The rich are able to hire accountants or lawyers to find loopholes in the tax code, so they generally pay less than the stated amount. With a flat tax, the rich end up paying a smaller percentage than the poor, which exacerbates the other two problems, and eliminates the sense of fairness caused by a flat tax.</p></li>
</ol>