Well it is a matter of WHO is on the point of rebellion. The New Englanders of 1804 were just as wrong as the Southern ruling class of 1860 and with far more justification than them. After all Jefferson had destroyed their economy whereas the Slavers revolted before he even took office.
In either case, there was not the legal or Constitutional basis to secede.
“Justification” depends on perspective. The south was obviously angry enough to start shooting.