Once someone understands marginal utility [of money], they'll understand that regressive taxes are probably one of the most unfair way to tax people.
Regressive tax
A regressive tax is a tax which takes a higher percentage of tax revenue from those on low incomes. As income increases, the proportion of your income paid in tax falls.

Suppose there is a poll tax of £3,000 (paid regardless of income)
In this case, the person earning £10,000 is paying
30% of their income in tax £3,000
Someone earning £30,000 is paying
10% of their income in tax £3,000
Someone earning £100,000 would pay just
3.33% of their income in tax.
Examples of regressive taxes
1. Gambling taxes – Those on low incomes have a high propensity to spend money on gambling and therefore pay a higher percentage of their income on gambling taxes.
2. Excise duty. Those on high income may spend more on petrol, but it is unlikely to be too significant, therefore as your income rises, the percentage of your income going on petrol tax is likely to fall.
If i were rich I should love a regressive tax plan.....
The idea always sounds appealing — at least I thought it did…read on — because everyone, present company included, hates the complexity in the tax code, and its proponents sell the flat tax as the perfect antidote.
Unfortunately, it’s far from perfect and in any real-world incarnation would be a lot worse than the current code on at least two key dimensions: fairness and fiscal. It’s a highly regressive tax that would mean the loss of gobs of revenue.