TL;DR: You waived your hands like OP, but it's still not a magic trick.
Taking 50 percent from Bill Gates reduces his power almost by 0. Taking 50 percent from that single mother? Her kids are homeless. The same tax level is not simply the same for all people. Flat tax is an idea for the rich, by the rich, disguised as an idea for the people, by the people. Like *most* American politics.
Sincerely, Owner of a custom PC-based $300 Ambilight system for 7 years. It makes a huge difference.