Actually, he is correct, if you change one word. It was not the South’s reaction, but the leading families of the South, who had the political and financial power endangered, who reacted. They were trying to keep their elitist position in control, while fanning the flames of Southern Pride with the people who, for the most part, didn’t own slaves and didn’t live like the leaders lived.
If slavery had ceased, their lives would not have changed, but the lives of the political and controlling elite would have changed drastically.
Slavery issue was an excuse and not a cause.