The south society wasn't on the same page as northern society and it was not something that could've been avoided.
No way. The South and the North quarreled over many things. There was absolutely no way that they couldn't have settled this unless they engaged in combat.
The two sides were in opposition most of the time and their respective cultures were out of sync with each other, with respect to each side's aspirations and morals.
Even if the north and south agreed on slavery. They still would have fought over states rights and national rights ( see Morill taxes)