Oh no he didn't... ('Free' to Choose)

Can someone please explain this passage of the Friedman to me?:

"As a result, the century from Waterloo to the First World War was one of the most peaceful in human history among Western nations, marred only by some minor wars - the Crimean War and the Franco-Prussian Wars are the most memorable - and, of course, a major civil war within the United States, which itself a result of the major respect - slavery - in which the United States departed from economic and political freedom." - page 52

Is he saying that slavery itself was a departure from economic and political freedom, and the Civil War was the result of (violent disagreements over) slavery? Or is he saying that the end of slavery was the departure from economic and political freedom (inasmuch as slaves were considered private property, the policies that the Civil War enforced on the South were tyrannical impositions on the free market in which slaves were an important commodity)?

Because I can really see it going either way, which is to say, I think this guy just really did just make a free-market argument against the abolition of slavery.