It's also entirely possible to read the motivation of the Republican party as representatives of a new industrial-urban bourgeoisie rising up against the established postcolonial plantation bourgeoisie and wanting to repatriate an increasingly restive black population once it can be replaced with the latest generations of new immigrants. At least that's how Settlers puts it.

Edit: That's obviously not to say they weren't justified in abolishing slavery, or that celebrating John Wilkes Booth isn't among the grossest, most racist, "let's go back to the plantation" shit you can pull as a party, and i'd argue that the North acted way too mildly against the plantation owners after the war as well. Just saying that on the level of political decision makers, it may be impossible to find a non-racist side here.