Er, . . .time out guys.
It is true that South Carolina fired the first cannons. (Since they did so only because Lincoln was sending warships into their harbor to reinforce a federal fort in their waters, one can debate earnestly who really started the War.)
But what this current argument forgets is, that South Carolina was not "The South". It was one small state in the South. The others didn't shoot first. And, the largest Southern States on the border had not even voted to secede, hoping for a peaceful solution.
Lincoln then ORDERED them to provide troops to the federal government, so that the North could send an invasion force of 75,000 men into the states that had already pulled out, but primarily South Carolina. Heck, Lincoln hoped that he could dupe Col. Robert E. Lee into leading it, so that he could make the political claim that a Southerner was leading the invasion. He was really upset when Lee refused and resigned from the Army.
Lincoln then made it clear that any State that refused to provide the required troops would be invaded and occupied. (Take a look at what he did to Missouri! And all they did was declare themselves neutral!)
I believe that that, in a nutshell, is why its called the War of Northern Aggression. Jefferson Davis did NOt send an army across the Potomac to attack Washington. He sat their, for months and months, negotiating for a peaceful resolution, and sure enough, Lincoln invaded Virginia with a huge force. (They weren't there long though. Got their butts handed to them at Manassas, and all ran back across the bridges into D.C.)
So, a little more complicated than the question of who fired the first cannon in S.C.
Mannyrock
Lincolns decision to invade, demand for troops, and forma threats to any State that refused to provide troops, were the express reasons for the larger border State's seceding.