...which has nothing to do with protecting them from any violation of their "negative rights." Accept that the Post Office is a government monopoly supported in part by tax money. Taxes are theft.
Also the recent proliferation of private carriers points out that there are much better ways, cheaper too, to move the mail.
Maybe so, but as a Constitutionalist I agree with the Founders that congress has this power. The Constitution also clearly grants Congress the power to lay and collect taxes.