It was recognized as a necessary evil at the time, and the justification for the ratification of the Constitution with slavery is that any alternativ… - Harry V. Jaffa

And Lincoln pointed out that this argument—which the Court applied to the territories—could also equally well be applied to the states, so that the prospect of slavery becoming national, not only through the spread into the new territories but in the spread to the states, was very great. This was Lincoln’s argument.

The motto of the United States is "e pluribus unum", or "from many, one." Originally, this referred to the one union formed from the many states. It became the motto of the country because we had to fight a great civil war to prevent the manyness of the states from destroying the oneness of the union. What led manyness nearly to destroy oneness was the presence of slavery in many of the states. The diversity that tolerated the difference between slavery and freedom had become intolerable. A crisis had been reached in which, according to the greatest American, the house divided had to cease being divided. It had to become either all free or all slave.

It is only with this prelude that the Declaration of 1776 proclaims the right to revolution. The people do not have an indiscriminate or uncontrolled right to establish or to abolish governments. They have a right to abolish only those governments that become "destructive of these ends". "These ends" refers to the security of equal natural rights. It is only for the sake of security of these rights that legitimate governments are instituted, or that governments may be altered or abolished. And governments are legitimate only insofar as their "just powers" are derived "from the consent of the governed". All of the foregoing is omitted from South Carolina's declaration, for obvious reasons. In no sense could it have been said that the slaves in South Carolina were governed by powers derived from their consent. Nor could it be said that South Carolina was separating itself from the government of the Union because that government had become destructive of the ends for which it was established. South Carolina in 1860 had an entirely different idea of what the ends of government ought to be from that of 1776 or 1787. That difference can be summed up in the difference between holding slavery to be an evil, if possibly a necessary evil, and holding it to be a positive good.