The gigantic problem with these types of arguments is that it ignores, and by necessity it has to ignore, the single biggest piece of evidence. When the Civil War started it was NOT between the Union and all slave holding states. A number of slave holding states fought on the side of the Union. The Civil War was between the anti-succeeding and the succeeding states. The primary issue was succession.
It is a good thing the Civil War resulted in the end of chattel slavery in the United States. Chattel slavery is evil, and the United States at its founding was steeped in it. As a country we need to believe the lie that we fought the Civil War at the cost of hundreds of thousands of lives to right that wrong.
Seceding and secession.