LOL, your */~rdavis whoever he is, constructs a strawman, and does a lousy job of analysis.
rdavis is a fellow Freeper named Remember (AFAIK). You can take up his analysis with him. He seems to have done a good job to me.
Good then he will be able to explain his methodology used to isolate the effects of changing marginal rates on avoidance behavior that causes the laffer curve to turn down as the maximum tax rates approach 100% and how tax avoidance behavior decreases as the marginal rates decrease providing higher revenues as marginal rates decline toward providing a nominal peak of revenue.
For the Laffer curve is a composite of two effects arising from limiting conditions on a taxed population, tax rates interacting with tax avoidence, limiting revenue extraction. The more you tax a thing the less it will be indulged in by those who are taxed.
High marginal tax rates hitting the most prolific earners increases their propensity to avoid the or shelter from the tax, set rates high enough taxpayers cease to produce or depart for a more tax friendly environments.