What this tells me is that you have no grasp of the economic realities of the Southern States in the 1860s. Their economic engine ran on Agriculture and it's heavy dependence on slavery.
It is not a trivial comparison. Today our economic engine runs of fossil fuels. To them (And You really need to learn to comprehend the concept of "zeitgeist") this would have been very similar to shutting down 1/4th of our economy.
Ignoring the human component, which the Union also did as long as it suited their interests, the economic and assets of that industry were simply too big to eliminate without much upheaval and destruction to their economic condition.
We modern people have just become accustomed to looking at things from a prism of modern ideas, and many of us have no comprehension of what things looked like to the people involved.
If gay marriage stands, a hundred years from now, indoctrinated people like you will be regarding us all as barbarians for not having legalized it sooner.