This is really a stupid statement. Enshrined is enshrined no matter how you wish to describe it. It's like it makes a difference how someone is murdered. The murderer is STILL the murderer.
Except that, to use your analogy, what constituted murder under the U.S. Constitution did not constitute murder under the Confederate one. The U.S. Constitution did not protect slave imports, the Confederate Constitution did. The U.S. Constitution allowed states to outlaw slavery, the Confederate Constitution did not. The U.S. Constitution allowed Congress to decide if slavery would be allowed in the territories, the Confederate Constitution mandated slavery's legality in any territory the Confederacy acquired. The U.S. Constitution would allow for the end to slavery via Constitutional amendment, but even had the Corwin Amendment been adopted it would also be impossible to end slavery through Constitution amendment in the Confederacy as well. There was a great deal of difference on how both documents dealt with slavery.