Amen! Slavery was in contradiction to the principles of the Declaration of Independence and that was the subject of the Lincoln-Douglas debates.
This is completely incorrect. Jefferson wanted anti-slavery commentary put into the Declaration of Independence, but he was outvoted by the committee, and they stripped out the vast bulk of his anti-slavery language.
They did leave in his "all men are created equal" statement, but they did not in any way at that time endorse the idea that this was intended to apply to slaves. In 1776, they intended those words to only refer to white people, though later people started to assert that this principle should also apply to slaves.
In 1776, all the states were slave states. There were no "free states" at that time. The idea of making states into "free states" came later, and in my opinion, greatly as a consequence of Jefferson's words, and the acquiescence of the continental congress in leaving them in the document.
But to assert that getting rid of slavery was intended by the Declaration of Independence is just incorrect. It was not at all intended at that time. This was a later, "creative" interpretation of the document.
The sole purpose of the document was to assert a natural law justification for breaking away from England, and there was absolutely no intention to speak on the issue of slavery by the Continental congress or the states which they represented.
That is a later created claim which is in fact incorrect.