Add to that, the 1860 election where the southern people saw no hope of a resolution to the situation and were not encouraged by the Lincoln/Republican campaign. And saw him as supporting the abolishionist, who had supported that raid, in spite of his rhetoric of neutrality on the slave issue.
THEN, after the election of Lincoln in November of 1860 you almost immediately have the "in-your-face" provocations of Winfield Scott stationing federal troops at arsenal throughout the south where there had previously been no need of such garrisons. How else were the southern people supposed to see these provocations except as a dagger pointed straight at the southern peoples throat?
Instead of the rights of the southern people being protected by the Federal Government it was obvious to all that the Lincoln adminstration was placing "land mines" in the midst of the southern people to trigger an incident by which a war could be declared against them. Everybody in the south saw Fort Sumter for what it was, the 1832 Nullification Crisis all over again, and the "Star of the West" incident only reinforced that opinion and caused 6 additional states to seceed. THAT was the "Tipping Point", not Kansas being admitted into the Union.
There would have been no war If the United States Government had not provoked it. It was Mr. Lincoln's War.
What is really funny now is that today people are talking once again about "States Rights", and "Nullification" and "Secession". Isn't that odd? We are not talking about the slaves this time.