Sure he was. And then he continued with those stirring words, "I believe this government cannot endure permanently half States Rights and (in a related note) slavery and half without States Rights and (in a related note) slavery. I do not expect the Union to be dissolved -- I do not expect the house to fall -- but I do expect it will cease to be divided. It will become all one thing, or all the other. Either the opponents of States Rights and (in a related note) slavery will arrest the further spread of it, and place it where the public mind shall rest in the belief that it is in the course of ultimate extinction; or its advocates will push it forward, till it shall become alike lawful in all the States, old as well as new -- North as well as South.
Give it up. The division was over slavery. State's rights didn't enter into the picture except as an excuse to support slavery's spread.
Yes, slavery was the "camel that broke the straw back" to use Fred Flinstone's immortal words. But there was also the issue of whether the individual states would be allowed to decide for themselves, or whether dictum would come down from D.C.
(What concerns me right now is that human slavery is still practiced by Muslims over animists and Christians in Africa, and in the child sex trade in a number of places...we need to eliminate those TOO.)