Luther is an ass for making an argument? I didn’t see anything insulting or disrespectful about anything Luther said. It was Jon Stewart that was making the jokes. All Luther did was quote a passage from the Constitution. He could be wrong. Krugman could be wrong. None of the bills or coins used as a medium of exchange are issued by the federal government. They are Federal Reserve notes. The Federal Reserve is a bank. US currency is backed by the credit of that bank.
Which is backed by treasury bonds sold as debt, which is backed by the ability to tax the productive output of the citizens.
The Federal Reserve backs currency with your belief that the currency is worth something. That’s all. Krugman’s proposal that a $1 trillion dollar coin (or note) could be issued is quite accurate. His proposal that it be made of platinum is nice but it is not required. The 1995 law he was thinking of is actually obviated in this case by the 1933 Emergency Banking Act which set the legal framework for this statement by the Treasury:
https://www.treasury.gov/resource-center/faqs/Currency/Pages/legal-tender.aspx
“Federal Reserve notes are not redeemable in gold, silver or any other commodity, and receive no backing by anything This has been the case since 1933. The notes have no value for themselves, but for what they will buy. In another sense, because they are legal tender, Federal Reserve notes are “backed” by all the goods and services in the economy.”