[ancient_geezer]

Why do you figure it would be any more easy for them to do it under a general sales tax, that it is now when there is no sales tax to put such a tax on top of.

A sales tax in place would act to impede such activity more than the current situation.

[Myrddin]

When the only tool you have is a hammer, everything starts looking like a nail. If the only means of taxation and social engineering is via targeted retail taxes, you will see a proliferation of special retail taxes. Instead of a progressively punitive income tax, the politicians will take aim at things "you don't need". Guns, SUVs, boats, tobacco, alcohol...pick your favorite target of social demonization.

Increasing a general sales tax might well be more difficult. A targeted sales tax that goes after items that are only accessible to people with substantial disposable income (aka "the rich") would not cause a general outcry. How many people complained about the "luxury tax" on large boats? Almost nobody. The "rich" responded by not buying the boats. The boat manufacturers responded by folding up shop. The idiots who foisted the tax on the boat "consumers" made less money and put lots of boat manufacturing workers on the street. The failed tax attempt was later rescinded.