Consumption tax, consumption tax, consumption tax. Way, way better. Much harder to avoid paying. The wealthy will pay more because they consume more. Currently if one donates to enough politicians one can have a complete tax exemption for oneself written into any bill at all... So a lot of small businesses don't pay anything. Large businesses don't pay anything, they use politicians to get corporate welfare. Those things won't change with a flat tax. With a consumption tax calculated at the point of sale manufacturing an exemption would be impossible. How are you going to get that into the software of all the terminals? The IRS could go after people that were not forwarding tax they collected instead of the people not paying it and thus kill many birds with one stone.
Consumption tax is just a very practical answer to a complex problem therefore every know-it-all-introvert-academic will hate it, people on the left will hate it and find a negative term for it like "regresssive" and shout down anybody that mentions it, maybe firebomb them etc...
I'd love it if Donald Trump came out in favor of consumption tax replacing the income tax. He could challenge the privacy advocates to fight intrusion by the IRS at tax time. Hee hee, the ACLU is against police asking criminals questions but they never say anything about the IRS asking all the invasive questions they demand answers to.