Whether or not a college educated person earns the same or more than a non-college educated worker depends on a number of factors. I know college educated people who earn less than plumbers or electricians.
If someone earns more, they should pay more in taxes, regardless of source of income. If they earn less, they should pay less, regardless of the source of income. Tax rates, if they vary, should be tied to the amount of income, not the source.
I agree with the progressive income tax but I also agree with how FICA tax is handled. Generally speaking, people who will not collect social security later in life (railroad and/or government work) are not required to pay into FICA tax. In this same spirit, non-college educated workers should not have to bear any of the tax burden (or otherwise) for college degrees only benefiting those higher value workers. Its just not fair to those people. Because in the final analysis, everything that is free is paid by people who work.
In the same spirit, it is not fair non- farmers have to pay taxes to support farmers, or childless people pay taxes to school children, etc….
Moreover, education benefits society in general, so taxpayers do benefit.
Finally, since money is fungible, how on earth would you be able to insure some group’s taxes do not end supporting this?