That is no more important, no more “key”, than the phrase “as to them” shall seem most likely to effect their Safety and Happiness.
A state does not have to have permission to declare independence - that is the reason it is referred to as a Declaration of Independence.
A more logical argument, from your point of view, would be to say the Confederates didn't know what they were talking about because the Confederates were only the sons and grandsons of the founding fathers and never had the opportunity to learn history in public schools or watch television.
More strawmen from you. You’re not very good at this.
“A state does not have to have permission to declare independence...”
A state can do whatever it pleases. That does not free it from the consequence of poor choices. The con-fed slavers chose poorly and paid a horrendous price.