Just what diplomatic solution did you want Lincoln to arrive at. What was he unable to do? By the time he was inaugurated seven states had already seceded (or so they declared). LIncoln reached out to those states (and the other's leaning that way) in his 1st Inaugural Address. He said he had no purpose to interfere with slavery where it existed (in all of the states that had seceded). He had held that point all the way back to his debates with Douglas in 1858. He pointed out, in his address, that any civil war (he rightly refused to recognize secession) was in the hands of those "dissatisfied" states.
Their actions were the cause of the civil war, not Lincoln's.
He raised an army, but southern states had already raised a variety of militias for the purpose of protecting their right to secede. He had just swonr to uphold the Constitution. Was he to ignore that oath?
Lincoln was a tyrant? Come again? He forced no northern state to resist southern secession. He forced no war on the nation. When he called for a draft it was in need of an act of congress. He might have simply let the southern states secede, something the Constitution provided no mechanism for, nor any mention (he rightfully considered it as unconstitutional).
When he "marched on his own citizens" he did so in order to protect the union. It was their act that attempted to destroy it.
The right of the states to "self regulate" (using your words) was and is limited of course. It in no way allowed states to simply drop out of the union because they were unsatisfied with the course of politial rivers. Should Alabama be allowed to secede today becasue they disagree with the course the Obama administration is moving the nation?
To be consistent, you must believe that they should be allowed to and that nothing should be done to prevent (beyond diplomacy that may or may not work) such an action.
We accept Lincoln's greatness because he was indeed great.
His Emancipation Proclamation occured a year and a half into the war. Until then, he had made no statement about ending slavery where it existed...and when he did issue that proclaman=tion he did so with the greatest of diplomacy, not "freeing" (the proclamation essentially freed almost nobody. Union soldiers did that) the slaves in the border states Missouri/Marlyland/Kentucky/Delaware) that remained in the union. It was an acto of necessity...and great wisdom. Lincoln understood that no southern slave owner would free slaves because he declared they should do so, but he also knew that the war needed a higher cause....were the north to stay the course. That was an act of supreme diplomacy, realpolitik, and may have held the nation together.
Ah....I will stop now. On and on I could go.