Perhaps you read someone else's post and responded to mine on Northern sentiment during the 1850s. If not, you're avoiding all points made in the quote from Forrest McDonald's book. Questions raised in that quote had nothing to do with the historical basis of slavery or the institution being illegal or not or who was at fault for the war. In 1854-55, the war was an event in the future. Prior to the Kansas-Nebraska debate, people in the North generally thought abolitionists were radicals and accepted slavery as a Southern institution.
Also, contrary to your posts, Southerners used the Federal government and the U.S. Constitution as their first line of defense. Opponents in the North resorted to the States Rights position or to a "higher law", something above and beyond the Constitution.