A Constitutional Amendment makes something law that cannot be overturned by Congress. It can only be overturned by the Supreme Court. That is why the Far Right wing wants Constitutional Amendments requiring prayer in schools, limiting the rights of gays and outlawing abortions.
Every argument against the 16th amendment’s constitutionality has been denied by the Supreme Court. Tax scofflaws may want to claim sovereignty or some kind of belief that they can pick and choose what laws they will recognize. However this is a nation of laws, not men. Under the theory of social contract we give up some liberty, including putting ourselves above the law, in order to share in the protection and benefits of citizenship.
Personally, I am satisfied to pay taxes even though I probably pay a greater than average amount (single, middle class, standard deduction) and I am willing to pay more in the near term if it will put people back to work and the money is not being wasted on useless wars. (Even then I will work to get us out of the wasteful activity and not withhold taxes-that’s so passive-aggressive) The more people who are working in the long term, the less my burden.