Income Tax Unconstitutional?

Here's a thought that just popped into my head the other day, and I don't have an answer one way or another, so I was just wondering all of your thoughts on it.

Is income tax unconstitutional? Full disclosure, many of you know that I would personally favor a national sales tax, or FairTax, as opposed to income tax (I'll probably make a post about that at some other time), but I'm not really trying to push for one or the other in this post. I'm just looking at the idea of income tax in a new light, because taxation is taxation in one form or another, and whatever way we accomplish it, we can still have the argument over how much we should be taxed, so I don't really see this post as a partisan post.

First off, here is the 16th Amendment to the U.S. Constitution that explicitly allows for income tax collection:

"The Congress shall have power to lay and collect taxes on incomes, from whatever source derived, without apportionment among the several States, and without regard to any census or enumeration."

Pretty explicit, right?

What I'm thinking is that the 16th Amendment goes against the 14th Amendment (amended prior to the 16h), specifically in the first line. (The rest of the Amendment deals with abolishment of slavery, which gives us keen insight to the intent of the 14th Amendment). Here's the first part of the 14th Amendment, which deals with equal protection:

"All persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States and of the State wherein they reside. No State shall make or enforce any law which shall abridge the privileges or immunities of citizens of the United States; nor shall any State deprive any person of life, liberty, or property, without due process of law; nor deny to any person within its jurisdiction the equal protection of the laws."

I specifically put "equal protection of the laws" in bold, because doesn't income tax go against that? It is specifically discriminates against citizens based on their accumulation of wealth. As in the context of the time, former slaves were being singled out simply because of their skin color and not given the same rights to life, liberty, and property. Fast forward to today, wealthier individuals are being singled out to "deprive" them of economic liberty and property (money).

Would not a flat tax or a flat sales tax grant more equal protection under the law, in that every citizen is subject to the same taxation rate under the law without discrimination?

For the poor, they (we) naturally pay less tax anyway, because either under a flat tax they make less income and are therefore taxed less, and with a national sales tax they buy less and buy cheaper items. Those are individual experiences outside the law, which under a flat/fair tax applies to all equally, and individuals are free to move up and down without any discriminatory change.

It is not the law's job to discriminate on any basis, but to afford equal protection to all individuals.

Here's another thought. If my argument were to be valid, that means that two parts of the U.S. Constitution conflict with one another (the 16th and 14th Amendments). What does that mean? Say, for simplification purposes, we pass an amendment that states, for example, "be it here deemed, capital punishment shall hereby be a legal and just means of disciplinary action in the United States."

Say 20 years later, we pass another law stating the opposite: "be it here deemed, capital punishment hereafter is found by the Congress and President of the United States to be an illegal and harsh means of disciplinary action in the United States."

This is just a side thought, but does the latter automatically invalidate the former, is there a repealing process? Any law students or more knowledgable people may be able to help me with this.

I would appreciate any thoughts on these ideas I was kicking around!