setting up a debate over whether the southern succession was about slavery or states' rights is a false dichotomy, as slavery, in a nineteenth century historical context, is an example of states' rights. succession can be largely about slavery and still be fundamentally about states' rights.
nor is it necessary for the north to be opposed to slavery - it wasn't - for succession to have been about slavery. the bankers in the north may have wanted a larger share of the profit.
generally, academics don't seek to find singular causes for complex events, they look towards multiple factors and narratives. so, why is there such vehement reaction to anybody that dares to extrapolate on the idea that there were other causes of the civil war than slavery, when the same people will take complex and subtle views as to the cause of, say, the revolutionary war, or the world wars of the twentieth century? the reason is that it became connected to a kind of founder myth during reconstruction. the elite tried to build a national identity around abolition and they wanted the civil war to be a triumph of good over evil that was won by good god-fearing christian soldiers. any questioning of this myth become convoluted with a kind of treason, and suspicion of sympathies with future rebellions.
slavery certainly had a lot to do with the civil war and anybody arguing otherwise is being daft. but it was merely a component of deeper class and cultural divisions and competitive pressures.
these debates don't bother me. but, i don't react well to being silenced or being told to adhere to a narrow or monolithic view of history at the exclusion of verifiable facts and evidence.