“We had the military strength to defend our secession, the South did not.”
Ok, the might makes right argument is sensible, but it’s beside the point if one is arguing about the viability of secession, since it can only be determined after the fact. There’s no way to know ahead of time if you will prevail with force of arms. It also bears no relation to whether the states have an inherent right to secession, since they can have a right to do it even if it’s not feasible for them to exercise the right without fighting a war.
It looks like to me that states have the right to secession, but they must run it through the Congress to prescribe the manner and then get terms of separation. Having a rabble-rousing rally and then going on a stealing spree doesn't qualify as a legal secession. If it's not done legally, then there must be the military might to make it stick. This was accomplished with the colonies, not with the South.