With the Dred Scott decision by the Supreme Court, the passing of the Corwin amendment in March of ‘61 by the Congress, and Lincoln's endorsement in his inauguration speech, all of the branches of the United States government were aligned in support of legalized slavery.
Since the deep South had already seceded, there was no point in conflict as a moral issue.
I'm not following. Lincoln was elected primarily on his main platform plank of no slavery in the territories, and stated unequivocally (the first president to do so) that slavery was a moral evil. The Democrats, as headed by Stephen Douglas, had taken the exact opposite decision, that slavery was "individual choice" or, if one went with the leading southern spokesmen, that it was a matter of state law.
But no one thought that this meant that slavery would any longer be tolerated in the territories, and Lincoln was elected precisely because the Dred Scott decision was so morally wrong. And four slave states remained in the Union.