The Civil War: Why?

It's hard to argue that the Civil War didn't have a huge effect on America. It destroyed the infrastructure of the South, it created a lasting resentment across much of the area, and it provided a catalyst for the elimination of many Constitutional limitations on government, among other things. Southern political extremism still wields power over the United States and, to a great extent, the world.

Should the Civil War have been fought? Obviously no moral justification can be assigned to either side - both did too many horrible things for one to be justified. What would have happened if the Southern states had just been allowed to secede?

Had the Southern states been allowed to secede, the North and West could have gotten on fine without them, and as the South slowly decayed (their form of government was disastrous, and slavery was on its way out anyways), eventually the South would have wanted back in. Many of the current tensions consuming the country would have been avoided.