Consequentialism is the false proposition that the morality of an act is contingent only on its consequence. When it comes to the moral analysis of history, few events provoke as much consequentialist argument as the American Civil War. Both those who take the side of the Union and those who support the South make arguments based on the results of the war, often neglecting the actual actions and motivations of those involved.
Union supporters point out that the North's victory ended slavery in North America. This is true of course, but most northerners did not fight for emancipation, but for national union. In addition, slavery might well have been ended by peaceful means albeit later than it actually was. This does not mean that slavery should simply be ignored when examining the morality of the Civil War, but rather that an argument based on slavery alone is insufficient.
Yankees aren't the only ones who advance consequentialist arguments. Neo-Confederates like to point out that the federal government is ridiculously and unconstitutionally large and that the increase in government size started with Abraham Lincoln's administration. There are a number of problems with this idea. Most importantly, the Civil War doesn't have a darn thing to do with Obamacare, the EPA, or the National Endowment for the Arts. It's true that the North rejected states' rights at least as far as secession was concerned, and that Lincoln supported tariffs and federal highways, but northerners were not fighting for a federal welfare state and southerners were not fighting against one. Besides, even if one accepts the idea that the North's victory ultimately led to today's bloated federal government, it can serve only as a consequentialist argument in favor of the Confederacy.
The morality of either side of the conflict can only be judged based on the actions and beliefs of the actual participants, not on a result of the war, whether it be the end of slavery or the perplexing election of Joe Biden to high office. Consequentialist thinking is relatively harmless when applied to the past, but when a consequentialist turns his attention to present issues such as abortion, terrible evils are done "for the greater good." Those who avoid consequentialism in historical analysis can avoid it in personal moral judgments. In all things, do good, avoid evil, and entrust the future to God.