The modern justification for all of the bad things that were done in the Civil War is slavery.
It is for that reason that I address the bad things that were done in the Civil War by addressing how slavery could have been ended a different way.
And this is because that is what people have been taught. Information that undermines this view is simply not taught. Have you ever heard of the Corwin Amendment?
http://www.wbur.org/cognoscenti/2013/02/18/the-other-13th-richard-albert