A couple of points:
1. The progressive Federal tax system allows other taxes to be regressive and flat - some state income taxes, sales taxes, fica etc - this is not a coincidence.
2. "Hidden taxes" are regressive - Kraft pays federal taxes, and that is priced into every block of cheese.
3. You too can pay no Federal income tax! All you have to do is make no money! Who in a household that pays federal income tax would like to switch places with a household that pays no federal income tax?
It is right that everything worth doing is worth paying for - and it's better that everyone see exactly what they are paying so government is more accountable; it is wrong to assume that half the country is getting a "free ride" because they didn't pay any federal income tax.