An income tax is the worse form of taxation. A little less than 50% of the people pay little or no federal income tax. The rest of us pay the tax. In effect you have one group of people paying the bills for another group of people. This is a form of tax slavery that I feel is immoral. With a flat sales tax, everyone is involved in paying the bills of government. The cost of government would be kept under better control when every tax payer had to help pay for it under a flat sales tax. Marx & Engels supported an income tax in their Communist Manifesto.  Our Founding Fathers did not believe in a direct tax on people because it was detrimental to the liberty of the people. They favored a consumption tax.
https://nccs.net/1996-03-answers-to-americas-tax-problems