[NKP_Vet]

In his 1961 book The Legacy of the Civil War, Pulitzer Prize winning poet and novelist Robert Penn Warren wrote that “the greatest danger to slavery was the Southern heart.” This certainly reflects Robert E. Lee’s statement, “The best men in the South have long desired to do away with the institution of
slavery, and were quite willing to see it abolished.” (Thomas Nelson Page, Robert E. Lee: Man and Soldier, pg. 38)

In the same book Warren also said this about America’s fabricated “treasury of virtue:”

“The official story that the war was about the South’s desire to protect and expand slavery and the North’s determination to abolish it is not merely an error in academic history. The evidence against it has not been ignored so much as it has been suppressed. It had to be suppressed because it contradicts the legitimizing myth of the centralized nationalist regime that emerged after the war. Having been repeated so often it has come to be believed because of repetition.”

Robert Penn Warren

[BroJoeK]

NKP_Vet quoting: "The official story that the war was about the South’s desire to protect and expand slavery and the North’s determination to abolish it is not merely an error in academic history.
The evidence against it has not been ignored so much as it has been suppressed.
It had to be suppressed because it contradicts the legitimizing myth of the centralized nationalist regime that emerged after the war.
Having been repeated so often it has come to be believed because of repetition.”
Robert Penn Warren

Years ago, as a young man I was told I should revere Robert Penn Warren, but somehow never quite got around to it.
Your quote here suggests something of why.
Like many slavery-minimizers, apparently Warren looked at the fact that slavery had nothing directly to do with Fort Sumter or Lincoln's call-up of 75,000 troops to suppress the rebellion, and so Warren says in effect: "see, see, no slavery, not about slavery, nope, nope, nothing to see, no slaves here, move along, move along."

But secession was all about slavery and Civil War quickly raised slavery issues, beginning in Spring 1861 with "contraband of war".
Contraband lead to paid black workers, the 1861 Confiscation Act, 1862 Emancipation, 1863 enlistments of colored regiments and from 1864 on: 13th, 14th & 15th Amendments.
Those were all about slavery, even if Fort Sumter wasn't.

You disagree?