Complex sentence: Another argument raised is that because the federal income tax is progressive, the discriminations and inequalities created by the tax should render the tax unconstitutional under the 14th Amendment, which guarantees equal protection under the law.
Split into simpler sentences: Another argument raised is that because the federal income tax is progressive, the discriminations and inequalities created by the tax should render the tax unconstitutional. This is due to the 14th Amendment, which guarantees equal protection under the law.