Please find the section of the Constitution that says slavery is legal. States Rights is an ambiguous term; that is why we have an amendments process. I don’t know of a Libertarian who opposes the 16th Amendment. The states don’t have any more of the right to trample human dignity then the federal government does.
Not sure what that string of words was getting at but the US Constitution today and how it is applied is far better than it's been for most of our rather sordid history. It's not perfect. It's a work in progress.
It never was perfect, and yes, it is a work in progress. You go back and retcon the parts that are bad. Like not abolishing slavery outright. But if your going to increase the executives power, go back and do it through the Constitution, via passing an amendment.