Battle Cry of "Socialism"?

I just finished reading James McPherson's Battle Cry of Freedom. It is a great book that I highly recommend---a one volume history of the Civil War.
My edition includes an afterword written fifteen years after he wrote the book. The afterword includes an analysis of liberty, before and after the Civil War. McPherson notes the difference between positive and negative liberty--"Negative liberty, therefore, can be described as freedom from. Positive liberty can best be described as freedom to." McPherson claims that the Civil War promoted positive liberty by freeing the slaves (and depriving slave owners of their property) and that secession represented an extreme of negative liberty. Thus, positive liberty gains at least equal footing with negative liberty and that is a good thing and led to all kinds of other good things from the federal government.
My response is that liberating slaves is a very strong form of negative liberty, not positive liberty. Secession may be an expression of negative liberty but it is not granted in the constitution. Granted the federal govt became stronger, bigger, taxed more, etc but I don't see this as a rise of positive liberty. Lincoln and the feds did what was necessary to win the war--they weren't setting out to create a modern liberal utopia.
In my opinion the rise of positive liberty coincides with FDR and his boneheaded responses to the Great Depression. Now we have the rights to food, healthcare, education, medical marijuana etc (and, of course, with no attendant responsibilities). And the enforcement of such rights usually involve the depriving of someone else's property---but to then say that these rights are on the same level as personal liberty (i.e. a freed slave) is ridiculous.
One of the legacies of the Civil War is an extremely powerful federal government but that does not mean that the feds must then enforce a whole panoply of "rights" that Lincoln would be disgusted by.