[Gunslingr3]

Warning that the rebels should not fire on Ft. Sumter, Confederate Secretary of State Robert Toombs said: ""It is unnecessary; it puts us in the wrong; it is fatal,""

So firing on Ft. Sumter is what put them in the wrong, not secession. Step by step, you're coming around...

[Nanodik]

So firing on Ft. Sumter is what put them in the wrong,

I suppose if a hostile nation set up a base on Ellis Island, we would just politely ask them to leave and then ignore them if they didn't. Lincoln was spoiling for a fight and used Sumter to get things started. Sumter resulted in 0 casualties and the surrendering Union garrison was treated with utmost respect by the Confederates. This was played up back in the North to get political support for Lincoln's war.