You expected them NOT to note that it was the other side which violated the constitution? What they really hated was actually constitutional....namely the way they were economically exploited in favor of Northern business interests. The North offered slavery forever but did not offer to stop screwing them over economically. They turned down the offer. That tells you all you need to know about the real motivations of both sides.
The articles of secession, and the fact that slavery was abolished after the Civil War, tells me all I need to know.