Please see my last post. No, those people were clearly not the People, in and of themselves. If there were an Constitutional Convention, held by the process described in the US Constitution, that would have been "We the People." Good reason based upon faulty premeses is bad reason.
Three prominent members of the confederacy seceded by statewide popular referendum. They all indicated overwhelmingly that they wanted to leave. You can't get any closer to the people than that.