Wow, the lowest 20% of earners pay almost nothing in taxes. The top 20% bear, let's see, 69% of the tax burden. How horribly unfair.
Until you look at this graph:
Here we see that the top 20% may pay 69% of taxes, but they also suck up 50% of all the income. The richest fifth get half of the pie. How much of the pie do the lowest fifth get? Just 3%. How much of the tax burden should we expect them to bear?
Before you complain about how little some folks pay into the system, look at how little is paid to them.