You just said that the flat tax makes sense because:
1) Steady Revenue stream.
So you think it's a good idea to make individuals who cannot afford to pay taxes in many cases, pay the same as individuals who make lots of money and you think that this is a legitimate solution. Such a policy would only seek to harm society's most vulnerable. For one, for it to be feasible, it would have to occur at lower rates than currently exist for the most affluent because most of the country can't afford to have their taxes raised. So you're going to be reducing government revenue, which will mean more projects will go underfunded, and it will directly cut at the social welfare system from S.S., to school funding, medicare, etc. It would necessarily shift more money into the hands of the well-off and more money out of the hands of those that are worse off.