Whilst not agreeing totally with that Irish guy, I do believe he's right that it wasn't the central defining issue that is portrayed in modern times. The real issue for southern states was the right to cut independent trade deals with Britain and France, which mirrors what is happening now with Brexit. I also think he's mainly right that Lincoln really only cared about slavery when he needed blacks as cannon fodder.
Wrongo boyo.
The southern states had no right to secede nor to attack the Union.
Based on these two lies the opinion is worthless.