I'll happily denounce it. I'll also happily share a post-war statement from a man who was the nation's foremost denouncer of slavery for decades prior to the war. Seeing as they come from an abolitionist of irrefutable credentials and a libertarian (small L) philosopher of similar significance, what he had to say is particularly telling:
"The pretense that the "abolition of slavery" was either a motive or justification for the war, is a fraud of the same character with that of "maintaining the national honor." Who, but such usurpers, robbers, and murderers as they, ever established slavery? Or what government, except one resting upon the sword, like the one we now have, was ever capable of maintaining slavery? And why did these men abolish slavery? Not from any love of liberty in general--not as an act of justice to the black man himself, but only "as a war measure," and because they wanted his assistance, and that of his friends, in carrying on the war they had undertaken for maintaining and intensifying that political, commercial, and industrial slavery, to which they have subjected the great body of the people, both white and black. And yet these impostors now cry out that they have abolished the chattel slavery of the black man--although that was not the motive of the war--as if they thought they could thereby conceal, atone for, or justify that other slavery which they were fighting to perpetuate, and to render more rigorous and inexorable than it ever was before. There was no difference of principle--but only of degree--between the slavery they boast they have abolished, and the slavery they were fighting to preserve; for all restraints upon men's natural liberty, not necessary for the simple maintenance of justice, are of the nature of slavery, and differ from each other only in degree.
If their object had really been to abolish slavery, or maintain liberty or justice generally, they had only to say: All, whether white or black, who want the protection of this government, shall have it; and all who do not want it, will be left in peace, so long as they leave us in peace. Had they said this, slavery would necessarily have been abolished at once; the war would have been saved; and a thousand times nobler union than we have ever had would have been the result. It would have been a voluntary union of free men; such a union as will one day exist among all men, the world over, if the several nations, so called, shall ever get rid of the usurpers, robbers, and murderers, called governments, that now plunder, enslave, and destroy them.
Still another of the frauds of these men is, that they are now establishing, and that the war was designed to establish, "a government of consent." The only idea they have ever manifested as to what is a government of consent, is this--that it is one to which everybody must consent, or be shot. This idea was the dominant one on which the war was carried on; and it is the dominant one, now that we have got what is called "peace."
Their pretenses that they have "Saved the Country," and "Preserved our Glorious Union," are frauds like all the rest of their pretenses. By them they mean simply that they have subjugated, and maintained their power over, an unwilling people. This they call "Saving the Country"; as if an enslaved and subjugated people--or as if any people kept in subjection by the sword (as it is intended that all of us shall be hereafter)--could be said to have any country. This, too, they call "Preserving our Glorious Union"; as if there could be said to be any Union, glorious or inglorious, that was not voluntary. Or as if there could be said to be any union between masters and slaves; between those who conquer, and those who are subjugated.
All these cries of having "abolished slavery," of having "saved the country," of having "preserved the union," of establishing "a government of consent," and of "maintaining the national honor," are all gross, shameless, transparent cheats--so transparent that they ought to deceive no one--when uttered as justifications for the war, or for the government that has succeeded the war, or for now compelling the people to pay the cost of the war, or for compelling anybody to support a government that he does not want." - Lysander Spooner, "No Treason" 1870