I have no argument with this claim. It accurately states the Union objectives at the beginning of the war.
However, why didn't the Southern states have just as much right to their independence as did the colonies from Britain? Again, the declaration of Independence (our founding document) recognizes the right of people to abolish one from of government and create another to their liking.
--That whenever any Form of Government becomes destructive of these ends, it is the Right of the People to alter or to abolish it, and to institute new Government, laying its foundation on such principles and organizing its powers in such form, as to them shall seem most likely to effect their Safety and Happiness.
Because they had signed on to an agreement that tied their fortunes to the Union, an agreement which has no provision for withdrawal.
Yes, our founding documents recognize the natural right of rebellion. And the Founding Fathers recognized the difference between annoyances and intolerable oppression. The south suffered no intolerable oppression. Although they were perfectly within their prerogative to seek dissolution they had no right to do so unilaterally.
First of all, there was zero in the way of oppression from the Federal government upon the South. Repeat === zero oppression. The government in power at that time was pro Southern in sympathy. They had no grievance, let alone grievance that justified secession.
Secession was a long sought desire of the Slave Power beginning with Calhoon in the 1830s.
The election of Lincoln, who opposed the expansion of slavery was an excuse for the slave power to do what they wanted to do for 30 or more years.
If the South had gone through Congress and presented their justification for separation, they could have been successful, but the fact is that in making their arguments that might have convinced congress, they would likely lost the support of the non-slave owning populations of their own states.
In my personal opinion, if the southern states had made secession a political process -- i.e. used the same process for admission of the states in reverse -- they could have been successful. The North was a sick of them as they were with the North.
But... once you fire on the Flag, you rightfully have a problem.
Righto. So what are "these ends" that morally justify rebellion when the existing Form of Government becomes destructive to them?
The Declaration is essentially a moral document. The Founders could simply have declared their Independence and proclaimed their willingness to fight for it, and let it go at that. But instead they spent considerable time and effort to develop a document that explained why they believed what they were doing was right.
So what were "these ends?"
Why, the rights to "Life, Liberty and the pursuit of Happiness," held by "all men (who) are created equal."
The American Revolution was morally justified only because it was intended to expand human liberty, not just because the Americans were unhappy.
A revolution by group A to impose or increase their dominance over group B is therefore by definition not justified by the principles of the Declaration.
Secession was not done to enhance or expand "Life, Liberty and the pursuit of Happiness." Rather it was explicitly proclaimed by those seceding that they did so to prevent the threat of some of their people gaining those rights.
There is also the little bit about "Governments ...derive ... their just powers from the consent of the governed."
Blacks and slaves in the South were part of the governed. Denying them any human rights at all or possibility of gaining them meant that whatever powers the secessionists might exercise, those powers were not and could not be "just."
The Founders were profoundly knowledgeable about history. They were well aware that many of the revolutions of the past resulted not in an expansion of freedom, but rather in one group (usually the nobility) gaining unjust power over the rest.
They stated very clearly that such a revolt, which was what secession at bottom was, could never be a just one.