‘No, he fought it to preserve the Union and because war was the path that Jefferson Davis chose. The question really is why the South chose armed rebellion in the first place and defense of their institution of slavery was by far the most important reason for their decision.’
A quote attributed to Longstreet comes to mind;
‘We should have freed all the slaves, THEN fired on Ft Sumnter.’
Had they done so, I think America today would likely resemble Europe, with a half dozen ‘countries’.
Actually that quote should be attribted to the screenwriter for "Gettysburg" because that's were it came from. I've never seen any evidence that Longstreet himself never said anything like that in any of the biographies I've read.