Let me repeat my earlier question: How should American slaves have invoked and realized their natural right of self-determination?
Not an easy to answer question. Most slaves couldn't read and most were uneducated, so they could hardly have been expected to know what arguments to make, or to whom to make them. Revolt would have gotten them massacred.
I would suggest the best they could do is for those that could, to follow along the lines of Frederick Douglas. It would seem to have been a necessity for others to speak for them on their behalf, because most slaves were neither knowledgeable or in a position where they could be heard.
For people in their position and under those circumstances, the best they could do is to keep appealing to Christian philosophy. Of course, since the Masters were making money off of them, I very much doubt the subject would be tolerated for very long, especially if it was seen to be effective.
But why are we talking about slavery? Lincoln was willing to keep that, so as near as I can tell, the point is moot. If both sides are willing to agree to something, you move on to the real point of contention.