I'm from Boston,I have ancestors who fought against the Confederates,and even I won't swallow that prophaganda.
They fought to defend their homes and their way of life.
Could you explain what is meant by 'way of life' aside from slavery, or why it was that the Confederate states felt that the election of Abraham Lincoln would endanger that 'way of life'? And, no, "the ideal that the right to secede from the Union is an unenumerated right for purposes of the Tenth Amendment" is not a 'way of life'.
It is absurd to say that Southern states seceded in order to protect the right to secede, especially since the election of 1860 wasn't fought over the question of whether secession was legitimate. What then? Did the Republican victory in 1860 threaten the religious practices of the Southerners? Or the right to speak their accustomed language? Why did they secede, if not to protect the institution of slavery?