I have a rudimentary understanding of slavery in the south and the northern response.
My understanding is that the moral arguments were not what drove us to fight. The moral arguments were used to support the war. The States Rights angle was 'fed' to southerners in order to get them fighting, but the true cause was the economic threat abolition posed to the south.
The plantation system created a situation where only 5% of southerners actually owned slaves and the 95%'s American dream was to one day own one. Abolition would undo this system for the wealthy and the 95% resented a Federal Government who would 'dash' their dreams.
I don't know how correct this is, but what played the largest role in the war: the moral stance, the politics (states rights), or the economics of abolition?
Edit: I also wanted to add; Moneyed interests in the north wanted to see less of a oligopoly controlling prices so turning slaves into market driven farmers would end up more profitable for the North. Any truth to this?
More can be written, but you might want to start with the FAQ section "Causes: The Civil War and Slavery" , specifically the first, a comprehensive look, "Was the American Civil War about more than just slavery?" by /u/Georgy_K_Zhukov .
"abolition": that is covered by Georgy_K_Zhukov's discussion about Union war aims as a cause and during the first two years -- it starts midway through part 4
"economic threat": you might want to read "Was the average Confederate soldier a strong proponent of white supremacy?" by Georgy_K_Zhukov again about motivation. I've always been struck by the line "the South was not simply a society in which people owned slaves, but rather it was a slave society", followed by explanation of what they meant by that.
As for "only 5% of southerners actually owned slaves": please see some links at "What percentage of the US population actually owned slaves?" , pointing to answers by /u/sowser and /u/jschooltiger .
"oligopoly": edit: upon reflection, I don't have a solid statement to make.
This is not to discourage discussion. More questions, data, and debate are welcome.