I don’t necessarily think its an unfortunate fact, more of an irrelevant one. When certain northern states considered secession in response to fugitive slave laws, they had a right in doing so even though later on they prevented the southern states from doing so. If the Confederate government really did try to prevent a certain group from seceding from Tennessee than they were wrong in preventing them but still were right in their legitimacy to secede. The south wanted to preserve slavery, and they were wrong in that regard, but the legitimacy of secession was still right.
The idea of secession does not live and die with the Confederate government. They utilized the idea but did not create it. Whether they have a good image or not is irrelevant to justification of secession itself.