Utter rubbish and nonsense, first perpetrated by Confederate leaders themselves, but only after their war was totally lost.
Then they immediately set to work creating a whole new mythology, rewriting actual history, to make themselves appear the innocent victims when, in actual historical fact, they were the villainous perpetrators.
In actual fact, Southern Slave-Power Fire-Eaters declared secession, and formed a new Confederacy, beginning in December 1860 -- as they clearly declared -- to protect their "peculiar institution" of slavery.
Then they started war against the United States to both defend their own sovereignty, and to assault the sovereignty of Union states & territory like Missouri or Oklahoma.
After suffering total defeat, and unconditional surrender, they invented a lot of nonsense to justify what, in fact, cannot be justified today in any terms the old Slave Power actually used.
The North was not united behind Lincoln in his war.
The South didn’t have to invent anything. There are newspaper accounts from the period, political speeches etc. that declare what people thought, many of whom thought Lincoln was abusing his power. He even imprisoned newspaper editors, mayors, and civilians for simply speaking out in opposition to him.
And the Old Slave Power was the United States of America, and before that it was England, so it just depends on how far back you want to go to prosecute our forebears.
The USA didn’t seem to mind oppressing the Native Americans.
The poster soakncider points us to the root of his difficulties - abbevilleinstitute.org. I don’t know if you bothered with them - I did. They recite the unambiguous facts of history well enough to retain some degree of respect but they aren’t above creative revisionism to get over the sticky spots. Because they decline to play it straight down the center they’ll never earn credibility as an unbiased history site.