i'm sure pstall or jase could get into this further than i could... but it seems to me that when you raise tax on the lower class, you're effectively taking away income correct? Heritage foundation has their flat tax rate set at 28%. So if you're making $28,000 per year, you're actually making $20,000 per year. Now, maybe that's enough to live on... probably not like a human being... but you could not die... as long as you didn't have to go to the doctor or something. If you have to go to the doctor... well... the government is gonna have to pay. Anybody who makes below that amount, flat out can't survive... so if you don't increase wages you simply incentivize people to live off the dole, which eats up your net gains, if you shut down the entitlements in addition to a flat tax (which is what would happen,) you literally end up with a huge amount of second class citizens. People who are making $4.85 an hour with no benefits. $39 a day with no healthcare. That's not good for a society as a whole.
Now. Say you do raise wages... well then the companies who are hiring people are paying out more for the same labor. You can put any numbers you want into it and figure out the difference between tax and increased wages... but then in order to keep profits/shareholders/bonuses, you need to cut dead weight... so you fire an equal number of people as is required to get your bottom line back to where it was. It doesn't matter so much because demand is down on nearly everything except staples... so unless you're making cereal, bread, diapers or baby formula your profits are down simply by virtue of an extra 100 million people (who used to have expendable income) being thrown below the poverty level. Crime is up... so governments spend more on prisons and police... which further negates whatever bonus you got from the tax plan and the wealthy (who spend very little money) continue to do so and everything stagnates because 10% of the population simply cannot fuel the economy. If instead of a flat tax, this is a VAT, effectively the same thing happens except the rich simply spend all their money over seas in order to avoid it. The earth cracks open, velociraptors emerge and feast on the young. Cats and dogs living together etc etc.
i'm not arguing whether or not a flat tax is "fair" (whatever the f*ck that means in a capitalist society,) I am arguing that it's a very poor way of advancing a society.
TLDR: mmmbeans flat tax distopian future.