Ceceeding was not about tarrifs! The minute that the southern states found out about Lincoln's election, they began the process of leaving the union because they were afraid that Lincoln would end slavery.
As far as this story about voluntarily freeing the slaves and ending slavery in the United States, all one has to do is look at the Jim Crow laws and other things that were enacted along with the activities of the Klu Klux Klan after the civil war to begin to understand the feeling about negroes in the south after the civil war. Southern feelings about negroes went far beyond economics as they were believed to be inferior beings. And, that is an attitude held across some parts of America to this very day. Just look at the states who are trying to enact restrictgive voter registration and voting laws in states where there are Republican governors and state legislatures. We could go on and on about this but please remember that if this had been only about economics in the south the rise of the age of mechanization as exemplified by the cotton gin was already making the need for slavery obsolete. And, there is one interesting theory of history that states that slavery in some forms did not, for all practical purposes, end in some places until the civil rights battles of the 1950's and 1960's began. Blacks had problems getting good jobs, were held in obligation to the company store, were kept down by other means and generally did not see their economic situation began to change until affirmative action and other anti disciminatory laws were put in place.
IOVHO,
Regards,
Joe