A flat income tax with no deductions? Seriously? You know that'd benefit the rich. Right now, a lot of poor people pay no income tax. I pay no income tax. I just have to worry about self-employment tax (equivalent to FICA taxes for employed persons) and that's it. I don't earn enough to pay income tax, and I don't think I ever have. Came close while in college given my grants.
A flat tax that somehow benefits the rich? Wow, how did you arrive at that?
Let me see here. Under a flat tax I make X dollars and pay Y tax on them where Y = some% of X.
Another person makes 2X dollars and pays 2Y in taxes.
Uncle Money Bags makes 100X dollars (I hope I'm in his will) and pays 100Y in taxes.
You know, that really sounds very fair to me -- although truly fair would be that everybody pays the same amount of tax each year because everybody benefits the same from roads, schools and other provided services.
Anything else is punitive from envious people who hate that someone else had more than they do.
People are weird that way. Take the social experiment where the researcher offers you $50, which you can take or refuse. But there's a condition: If you take the $50 then I get $100. But if you take nothing then I get nothing either. While you'd think that it's a no-brainer that you now have $50 that you didn't have before, you'd be amazed how many people will refuse to take their money because someone else "unfairly" is getting more in the process. And that attitude carries over into other areas.