I agree that progressive taxes generate more taxes than flat taxes. . People with more revenue are able carry a bigger burden, therefore the government is able to tax them more and generate more income. It is conceivable that having a higher tax rates for higher incomes would decrease the frequency and volume of such incomes, but I think the net effect would be higher revenues. Especially in this economic climate with the huge wealth gap. It would be almost insane and callous beyond belief to have flat rates.
In theory a progressive tax would generate more revenue than a flat tax since it requires people who make more money to pay more taxes. In practice, however, the current tax code in the United States is extremely complex and often requires a hired professional to decipher it. This allows the more affluent members of society to hire a professional and find tax loopholes, allowing them to pay fewer taxes than a less affluent member of society when looked at in terms of percentage paid per dollar of income.