Consider a more slavery-friendly early 19th century, such that the free states feel the need to secede from the 'slave power'. After a war similar to the OTL civil war, the secessionist movement is crushed and placed under a reconstruction roughly similar to our own. The U.S. abolishes slavery in the 1890s or 1910s.
In this scenario, how would the Northern secessionist movement be seen today? As far as I can tell, current attitudes towards the OTL Confederacy is based both on their representation of 'slave power' and as traitors to the Union. How would perception of an ATL northern Confederacy be different with the same 'treason' aspect, but with the benefit of vindication in hindsight over the slavery issue?