On April 8, Lincoln notified Gov. Francis Pickens of South Carolina that he would attempt to resupply the fort. The Confederate commander at Charleston, Gen.P.G.T. Beauregard, was ordered by the Confederate government to demand the evacuation of the fort and if refused, to force its evacuation. On April 11, General Beauregard delivered the ultimatum to Anderson, who replied, "Gentlemen, if you do not batter the fort to pieces about us, we shall be starved out in a few days." On direction of the Confederate government in Montgomery, Beauregard notified Anderson that if he would state the time of his evacuation, the Southern forces would hold their fire. Anderson replied that he would evacuate by noon on April 15 unless he received other instructions or additional supplies from his government. (The supply ships were expected before that time.) Told that his answer was unacceptable and that Beauregard would open fire in one hour, Anderson shook the hands of the messengers and said in parting, "If we do not meet again in this world, I hope we may meet in the better one." At 4:30 A.M. on April 12, 1861, 43 Confederate guns in a ring around Fort Sumter began the bombardment that initiated the bloodiest war in American history. http://www.us-civilwar.com/sumter.htm
The above happened before you claim Lincoln "initiated" the war.
As anyone who looks at the facts knows, the official purpose of the war initially was to "restore the union". But clearly secession happened because of the dispute over slavery. Lincoln wasn't even inaugurated until March 5, 1861, and secession was already well under way. The original 7 states had already seceded. You only need to read the speeches of the secessionists to confirm that slavery was the underlying issue.
As for the fact that the Emancipation Proclamation didn't happen for another two years, that was strictly political. Lincoln was a smart enough politician to know that until he won a victory issuing it would seem like the desperation of a losing side. The Battle of Antietam was enough of a victory to allow him to do so. But that doesn't mean that slavery wasn't the root issue behind both secession and the war.
Your quote is a description of an armed confrontation of an invading force....not an act of war by the Charlestonians.
The United States Supreme Court decided that the official beginning of the war began in Lincoln's office when he declared a blockade of Southern ports.
Secession occurred because of the failure of the Constitution to protect the states.
Lincoln invaded to retake Southern raw materials used in overseas trade.
Later, he and the press invoked the slavery rationalization due to the carnage problem.