His key point is the debunking of the common canard that “the Confederacy was about States' rights, not slavery.” He has a long quote from the “Cornerstone” speech on the subject by CSA Vice-President Alexander Stephens. Here's a juicy bit:
Our new government is founded upon exactly the opposite idea; its foundations are laid, its cornerstone rests upon the great truth, that the negro is not equal to the white man; that slavery — subordination to the superior race — is his natural and normal condition. This, our new government, is the first, in the history of the world, based upon this great physical, philosophical, and moral truth.
This is not Stephens' idea alone. Seceding states published descriptions of their causes and they are very clear. I have a few samples ready, for your convenience.
Our position is thoroughly identified with the institution of slavery
In all the non-slave-holding States, in violation of that good faith and comity which should exist between entirely distinct nations, the people have formed themselves into a great sectional party, now strong enough in numbers to control the affairs of each of those States, based upon an unnatural feeling of hostility to these Southern States and their beneficent and patriarchal system of African slavery, proclaiming the debasing doctrine of equality of all men, irrespective of race or color— a doctrine at war with nature, in opposition to the experience of mankind, and in violation of the plainest revelations of Divine Law.
an increasing hostility on the part of the non-slaveholding States to the institution of slavery, has led to a disregard of their obligations, and the laws of the General Government have ceased to effect the objects of the Constitution.
all the States north of that line have united in the election of a man to the high office of President of the United States, whose opinions and purposes are hostile to slavery. He is to be entrusted with the administration of the common Government, because he has declared that that “Government cannot endure permanently half slave, half free,” and that the public mind must rest in the belief that slavery is in the course of ultimate extinction.
That last calls for a rebuttal. I have Abraham Lincoln right here.
Judging by all they say and do, and by the subject and nature of their controversy with us, let us determine, if we can, what will satisfy them.
Will they be satisfied if the Territories be unconditionally surrendered to them? We know they will not. In all their present complaints against us, the Territories are scarcely mentioned. Invasions and insurrections are the rage now. Will it satisfy them, if, in the future, we have nothing to do with invasions and insurrections? We know it will not. We so know, because we know we never had anything to do with invasions and insurrections; and yet this total abstaining does not exempt us from the charge and the denunciation.
The question recurs, what will satisfy them? Simply this: We must not only let them alone, but we must somehow, convince them that we do let them alone. This, we know by experience, is no easy task. We have been so trying to convince them from the very beginning of our organization, but with no success. In all our platforms and speeches we have constantly protested our purpose to let them alone; but this has had no tendency to convince them. Alike unavailing to convince them, is the fact that they have never detected a man of us in any attempt to disturb them.
These natural, and apparently adequate means all failing, what will convince them? This, and this only: cease to call slavery wrong, and join them in calling it right. And this must be done thoroughly — done in acts as well as in words. Silence will not be tolerated — we must place ourselves avowedly with them. Senator Douglas' new sedition law must be enacted and enforced, suppressing all declarations that slavery is wrong, whether made in politics, in presses, in pulpits, or in private. We must arrest and return their fugitive slaves with greedy pleasure. We must pull down our Free State constitutions. The whole atmosphere must be disinfected from all taint of opposition to slavery, before they will cease to believe that all their troubles proceed from us.
I am quite aware they do not state their case precisely in this way. Most of them would probably say to us, “Let us alone, do nothing to us, and say what you please about slavery.” But we do let them alone — have never disturbed them — so that, after all, it is what we say, which dissatisfies them.
I first learned about Lincoln's Cooper Union address through Digby, who rightly notes that it remains very relevant to the political culture of our time.
Update: Sociologist James W. Loewen, of Lies My Teacher Told Me fame, offers a quick debunking of Five Myths About Why The South Seceded at the Washington Post, and Tracy Thompson at Salon explores the history of efforts to lie about the history of the Confederacy.
J. J. McCullough takes a close look at the Confederate constitution.
And Ta-Nehisi Coates manages to make the points I was going for in this post better than I did in his essay What This Cruel War Was Over, which even manages to out-geek me by including an X-Men reference:
Thus in 1861, when the Civil War began, the Union did not face a peaceful Southern society wanting to be left alone. It faced an an aggressive power, a Genosha, an entire society based on the bondage of a third of its residents, with dreams of expanding its fields of the bondage further South. It faced the dream of a vast American empire of slavery.
And Doug Muder says Please Take Down Your Confederate Flag.
I know you think your flag says something positive. But you need to understand that your intention does not control the message. You’re not saying what you think you’re saying.
Nobody enjoys being compared to the Nazis, but there is one way in which the swastika is an instructive example: It didn’t always mean what it means today. The swastika has a millennia-long history as a positive religious symbol. Even the word swastika has a pre-Nazi history, tracing back to a Sanscrit word that means good fortune. Particularly in India, you can see the hooked cross carved into temples built long before anyone ever heard of blitzkrieg or Kristallnacht or the Final Solution. There’s a lot in the swastika that I might want to invoke.
But I can’t.
The Nazis ruined the swastika. They own it now, because nothing captures a symbol like blood sacrifice.