Re: "data handed over is immune from freedom of information requests."
I believe income tax (which the 16th Amendment allowed by exempting it from existing restrictiong) was addressed separately from the matter of excise taxes. Income tax had been tossed around since the Civil War, but the Pollock case forced a resolution because SCOTUS got involved and limited income tax to that from labor (the states were supposed to get a proportional cut from income tax from other sources).
There had also been a discussion in the past about which was better: an income tax or a sales tax. They settled on the income tax primarily because it was harder to hide income under the table.
Biting the hand that feeds IT
