First, let me just say that it's rarely a pleasure for me to write a brief comment and get an essay in response, but I'm always glad to get one from you, and I appreciate you taking the time.

Having said that: no, I think you have this pretty much wrong. I took the time to read Sandefur's National Review article, and while I don't find much of what he writes persuasive, I also don't think his argument can be conscripted as cleanly as you suppose it can be.

Sandefur is a biographer of Frederick Douglass and writes about what F.D. believed to be a viable legal argument for constitutional abolition of slavery. Sandefur acknowledges that historians find many of these arguments strained; for instance: the Slave Trade Clause doesn't mention slavery, just "importation of persons", and the Fugitive Slave Clause mentions only "persons held to service or labor". That's interesting and all, but there's a reason the Fugitive Slave Clause is a proper noun: it was talking about slavery. Meanwhile: at the time, F.D.'s arguments didn't work. We had to fight a war to get rid of slavery. Lincoln had to preempt the constitution to eliminate slavery.

I don't dispute that compromise with northern abolitionists forced the framers to couch their language more carefully than they would have otherwise. But then: the author of the tweet you're talking about also didn't blot everyone's faces out. And the fact that there were convicted abolitionists among the framers makes it all the more notable that the document they ultimately ratified protected the institution of slavery, so much so that slavery had to be abolished by name in the 13th Amendment.

Your three-fifths compromise argument makes my point for me: as I said, abolitionists wanted slaves to count zero. Slavers fought to have their chattel property counted. Historians appear to accept that the result of this --- padding southern-state representation with slaves --- strengthened and prolonged the institution of slavery.

All of these arguments, by the way, seem reasonable! It's an interesting debate! My answer to "have Volokh and the National Review refuted the 1619 Project" is not the same as my answer to "have they shown the constitution of the Fugitive Slave Clause to be an anti-slavery document". But, more importantly: just the fact that we even have to have this debate, and to rewrite the story of US history most of us were taught as children, is a pretty strong indication that what we're talking about isn't a revolutionary reconsideration of the founding principles of the country.

Using the tools the framers gave us to bring the Constitution into line with our current principles isn't a refutation of the framers, any more than it was when we gave women the vote. You don't need to wait to demand a constitutional convention! Generate the support you need and do it now! That's the point of an amendable constitution.

(I don't think 2A is going to get amended at all, for what it's worth. But it's also the case that people smarter than both of us, including some who've sat on the Supreme Court, reject the way it's currently interpreted. I think it's a dumb amendment, and I love this country and its system of government.)