For your arguement to be valid, it must be a point of no slavery in the union, and slavery ONLY without the existing union.
If you'll take your blinders off, you'll readily see that it was the failure of the states to abide by their Constitutional agreement as the cause of secession. Slavery, whether practiced in northern or southern states, was an ECONOMIC issue, as the bulk of the economy was dependant upon it. It wasn't for MORAL issues that slavery was dying in northern states, it was simply economics, and the yankee desire to live in a land free of blacks. The Southern states simply got tired of subsidizing the Northern ones, and being bitched at in the process. The South simply divested itself of the nagging, sanctimonious yankees whose continual desire was to have their economy protected, unable to flourish against competition unprotected.
You have claimed, repeatedly, that slavery was NOT the cause of secession.
I have offered a mere sample of the various proofs that this is simply a lie.