It’s a fair point, and I don’t entirely disagree, except to say the working class pays more as a percentage of income–not in absolute amounts–for some of the taxes you mention.
Remember, though, that Social Security was not sold as a tax and in fact many of its supporters still pretend that it is not. It’s presented as a retirement account funded by Federal Insurance Contributions. They are, of course, payroll taxes, but the Big Government pretense is that these “contributions” go into a special fund set aside to pay beneficiaries such as the disabled and the elderly. The idea is that one gets back in proportion to what one pays in, much like a pension. Big Government being Big Government, they have long since spent all the money and there is no actual money sitting in a fund anywhere unless you count IOU chits.
But you’re right; it’s just a tax, like all other taxes. However, FICA taxes for the wealthy are small because the return is small–again, the idea is that SS is more of a defined-benefit pension fund…
For those arguing against removing the salary cap on SS benefits because its not fair when the payments are nearly the same for low and high income beneficiaries, this post by Ezra Klein has an illuminating chart. While the average life expectancy (at age 60) has increased relatively modestly over the past 30 years, the increase is by no means uniform by income. For the lower half of the income distribution, from 1972 to 2001 life expectancy at age 60 went up about 2 years. For the upper half, it went up by about 6 years. For benefits beginning at 67, the lower-income half would spend 12.6 years on SS, the upper-income half would spent 18.4 years. That’s 46% more time, and likely at a somewhat higher benefit level.
Either we should have income dependent SS benefit ages, or high-income workers should pay a lot more into the system.