We know exactly what Lincoln said about the matter as he wrote his opinion in his letter to Horace Greely.
The point that is trying to be made is that the war was started NOR engaged for the purpose of freeing slaves. Period.
The Federal government we are now slaves to was birthed by “the war of northern agression”. So the war was in one way about slavery.
The skin colors seem to have been swapped, but still labor is stolen by force to support the undeserving.
Obama stated often that marriage was to be one man marrying one woman. Did anyone believe this? Lincoln may have made statements about justification for war, but can anyone believe that he wanted slavery to continue?
A simple reading of the Constitution itself would prove just that.
The Founders put the service or Labor clause specifically under the authority of the States in the Fourth Article, not under the powers of Congress in the first Article.
The ninth and tenth amendments were supposed to further insure it was up to the States whether to have slavery or not.
Attempting to 'end slavery' by any branch of government was, in itself, a treasonous act.
From the North’s perspective you are right. It is undeniable that the South saw Lincoln merely as President as a threat to slavery. From that perspective, it was all about slavery and nothing else. Terrific book by Huston called “Calculating the Value of the Union:” South had more value in slaves than all the RRs and textile mills in the north put together.