Even though a dollar is worth a dollar, Dollars earned don't hold the same value all along the earning scale.
Look at it like this, imagine you're homeless and someone gives you a dollar. What is the first thing you do with that dollar? Buy food, maybe medicine, shelter or clothing. The basic life essentials. This is where mostly anyone would put their very first dollars towards. It's why you don't see homeless people saying "Will work for yachts". Those are items purchased with dollars further down the need scale. The first dollars anyone earns will be spent on basic life necessities.
This is why a progressive system that taxes these first dollars less and more heavily as the dollar has less value to basic life needs makes sense and doesn't put the poorest among us at a disadvantage. Is it perfect? No, but it's better than a mindless flat tax system that isn't fair to anyone but the richest among us.
Ok then why don't you answer the question in the OP
Why not make say the sales tax progressive as well after all that 3rd flat screen isn't worth as much to you as the first right? Why not make property taxes progressive and charge more for square footage you don't really need that is therefore worth less to you?
An earned dollar or any dollar of any type of income is nothing but a commodity like any other if we are going to have an income tax then we should tax income all income not some income not some dollars more than others
We do not do that for any other taxes levied on anything else
It's not the government's job to decide what people need
Why make one person pay 1000 dollars a year for federal government while some other pays 100,000 for the same government?
What makes that fair?
You are not taxing the person you are taxing the dollars of income
Everyone pays the same percentage on every dollar of income
The fact that one has more income than another is neither fair nor unfair
We tax at a higher percentage as there is more money to tax.
See, your premise makes no sense. You equate buying a new super yacht with struggling to pay the rent, insisting that we're not allowed to make any distinction in terms of the actual need of each because that's a subjective value judgment. And you're obviously wrong. As subjective value judgments are the basis of most every law. We not only can apply subjective value judgments in respect to our laws, we pretty much have to.
So the entire argument that the application of subjective value judgments invalidates progressive taxation is debunked. As we use the subjective value judgments on pretty much every law. And they're perfectly valid.
And while you personally may be incapable of recognizing the difference between say, a luxury yacht vs. paying the rent, a rational person could make that distinction. And rational people do. As progressive taxation is applied in pretty much every first world nation on earth.