Here is an article from the Atlantic in 2013 that I think everyone needs to read and understand before weighing in on this issue:
In recent years, historians have rubbed much of the luster from the Civil War and questioned its sanctification. Should we consecrate a war that killed and maimed over a million Americans? Or should we question, as many have in recent conflicts, whether this was really a war of necessity that justified its appalling costs?
Historians who came of age during the Civil Rights Movement placed slavery and emancipation at the center of the Civil War. This trend is now reflected in textbooks and popular culture. The Civil War today is generally seen as a necessary and ennobling sacrifice, redeemed by the liberation of four million slaves.
But cracks in this consensus are appearing with growing frequency, for example in studies like America Aflame, by historian David Goldfield. Goldfield states on the first page that the war was "America's greatest failure." He goes on to impeach politicians, extremists, and the influence of evangelical Christianity for polarizing the nation to the point where compromise or reasoned debate became impossible.
Goldfield sees slavery as the bedrock of the Southern cause and abolition as the war's great achievement. But he argues that white supremacy was so entrenched, North and South, that war and Reconstruction could never deliver true racial justice to freed slaves, who soon became subject to economic peonage, Black Codes, Jim Crow, and rampant lynching.
Nor did the war knit the nation back together. Instead, the South became a stagnant backwater, a resentful region that lagged and resisted the nation's progress. It would take a century and the Civil Rights struggle for blacks to achieve legal equality, and for the South to emerge from poverty and isolation. "Emancipation and reunion, the two great results of this war, were badly compromised," Goldfield says. Given these equivocal gains, and the immense toll in blood and treasure, he asks: "Was the war worth it? No."
Gary Gallagher, a leading Civil War historian at the University of Virginia, argues that the long-reigning emphasis on slavery and liberation distorts our understanding of the war and of how Americans thought in the 1860s. "There's an Appomattox syndrome--we look at Northern victory and emancipation and read the evidence backward," Gallagher says.
Very few Northerners went to war seeking or anticipating the destruction of slavery. They fought for Union, and the Emancipation Proclamation was a means to that end: a desperate measure to undermine the South and save a democratic nation that Lincoln called "the last best, hope of earth."
Gallagher also feels that hindsight has dimmed recognition of how close the Confederacy came to achieving its aims. "For the South, a tie was as good as a win," he says. It needed to inflict enough pain to convince a divided Northern public that defeating the South wasn't worth the cost.