What do you mean? Explain how a "progressive tax" system is promoting equality.
There is more than one way to look at equality, and how you frame it is certainly important. Framing it in the simplest way possible rarely gives you anything of substance with a complicated situation.
Here's an example: since money is really a place holder for goods/consumption, explain how someone having to sacrifice eating to pay taxes is equal to someone sacrificing one of five annual vacations to Aruba.
I don't actually lend much credence to the above argument, just as I don't lend much credence to a flat tax being the only form of equality.
If every American is taxed:
a% on their first $20K in income
b% on their next $50K in income
c% on their next $100K in income
d% on their next $250K in income
etc.
every American is treated equally under the law.
