I don’t see where there is a ban on congress having a sales tax. The are allowed to lay taxes (...The Congress shall have Power To lay and collect Taxes, Duties, Imposts and Excises,...)Art 1, Sect 7), the only restriction was on enumeration which the progressives turned over by way of the 16th.
But then why was there a need of the 16th Amendment to allow Congress to tax income?
An sales tax is an excise tax.
OK, but the next Constitutional question is, unless the 16th Amendment is repealed, what's to keep income tax from resurrecting after the sales tax is supposedly the only tax?