That's a really interesting read. I've taken excerpts from each state's declarations, in case anyone wants a state by state breakdown of their justification for secession

Georgia: "A brief history of the rise, progress, and policy of anti-slavery and the political organization into whose hands the administration of the Federal Government has been committed will fully justify the pronounced verdict of the people of Georgia."

Mississippi: "Our position is thoroughly identified with the institution of slavery-- the greatest material interest of the world"

South Carolina: "The right of property in slaves was recognized by giving to free persons distinct political rights, by giving them the right to represent, and burthening them with direct taxes for three-fifths of their slaves; by authorizing the importation of slaves for twenty years; and by stipulating for the rendition of fugitives from labor."

Texas: "She [Texas] was received as a commonwealth holding, maintaining and protecting the institution known as negro slavery-- the servitude of the African to the white race within her limits-- a relation that had existed from the first settlement of her wilderness by the white race, and which her people intended should exist in all future time."

Virginia: "…and the Federal Government, having perverted said powers, not only to the injury of the people of Virginia, but to the oppression of the Southern Slaveholding States.”