Furthermore, the central issue of the dispute between the northern and southern states was not preservation of slavery in the south. Only a minority of radicals in the north were actually pushing for complete abolition. Instead, the issue was whether slavery would be literally forced on the new territories and soon-to-be states in the west. The majority of people in those areas did not want slavery, and industry and labor in the north saw slavery as unfair and immoral competition. Equal accession of slave and free states was forced on the expanding United States in order maintain an even division of slave vs. free state representation in the Senate, and thereby maintain a level of power which their small population would otherwise not support, until Kansas and Nebraska upset that balance.
Secession, war, and eventual defeat stemmed from the desire of the slave holders to expand and spread their "peculiar institution". Appeals to the higher principles of "States' Rights" and "Freedom" were a thin cover for the fact that once the south could no longer get its way on the forcible extension of slavery, they decided to quit the Union altogether.
Whether they had the right to do so is a separate question. But I refuse attribute a high moral purpose to people who felt it was not only correct to hold humans as chattle but desirable to forcibly spread that practice to places where it was not wanted.
PS: The first shots of that war were fired by the south. Try shooting some artillery at Fort Bragg or Fort Campbell today and see how the Federal government reacts.