See my post at #112 about "defending" the Constitution.
About the Confederates attacking the North see #70. The Southerners had no designs upon the Northern States and it is a gross misrepresentation to suggest otherwise.
ML/NJ
Yet the Confederates did attack United States forces. Their designs were clear in that they were determined to disregard the Constitution and hold any United States citizen in their state enslaved.
The Confederates were trying to seceded from the Constitution unilaterally without any regard for the rule of law. They also fired upon U.S. forces.