Why did so many non slave owning, and most likely never to be able to own a slave, Southerns fight? Why did so many southern white laborers, in many ways their labor value suppressed by slave labor, why did they support and fight for their state?
Who cares what started the Civil war?
Damn the first man that brought a slave into this country. Damn him to hell.
Because they were Southron patriots, and because they didn't cotton to a Yankee Army invading their homes and ripping up their institutions?
Any white southern non-slaveholder had a vital interest in containing the violent and potentially violent African population which lived among them. The South did not practice Northern-style segregation. Africans were, at least in the Deep South, everywhere.
The North never gave, and has never given to this day, a coherent theory of race relations (a/k/a "diversity") which could persuade any sentient white Southerner exactly how what would happen AFTER emancipation would or even could be good for him and his family.
The southern white laboring non-slaveholder had every reason to fight.