[Kaslin]

I believe that is a matter of opinion if the income tax is constitutional or not as it was not established until 1909 and not by the founding fathers

[Taxman]

See The Law That Never Was: The Fraud of the 16th Amendment and Personal Income Tax, a 1985 book by William J. Benson and Martin J. "Red" Beckman which claims that the Sixteenth Amendment to the United States Constitution, commonly known as the income tax amendment, was never properly ratified.

[OIFVeteran]

The founding fathers established a way to change the constitution, the amendment process. So once an amendment is passed it is ipso facto constitutional.

Now you can make the argument that it is not something the founding fathers would have approved of and many would agree with you.