But the civil war was also about an issue just as big which was not avoidable, and that was the question of whether the US was going to be able to industrialize (which required tarrifs) or whether we were going to allow England to dump manufactured goods here and essentially continue using us as a colony.
You'd have to show by research, I think, that the Republicans had a coherent industrial policy in mind, one, and that, secondly, they made medicine to precipitate a constitutional crisis -- and win it politically or militarily -- which would allow them to recast the federal Union in such a way as to empower the federal government to impose that policy over the objections of the Southern States.
Which is what happened, so it isn't hard to argue that some farsighted Republican(s) might have entertained a long view even before the war, that anticipated much of what followed.
Which, if shown, would damn them as war criminals.