If I have been unrealistic I would say it was in assuming that the leaders of the parties seceding and the parties remaining were moral statesmen, not out to keep or acquire that to which they have no moral right, rather than gangsters out to get whatever they can acquire by whatever means. Perhaps that can be characterized as not "giving actual historical experience much weight".
However valid your characterization of my statement as "overly rationalistic" may be, you leave open the question: when some parties to a federation feel that their continued membership would be impossible for them and to their distinct disadvantage, what is to be done to achieve a just, and one would hope peaceful, resolution?
I don't think many would object if the discontented told the existing government that things weren't working out and some sort of separation would have to be arranged. Some might object, but a pacific, rational, moderate approach to separation would eventually have won out. But this wasn't the path the secessionists took. They felt themselves to be aggrieved and wanted to "act out" their anger. The saw themselves as the reincarnation of the revolutionary spirit of 1776. A false assumption, and one which encouraged them to take the wrong course.
Both sides wanted to win or keep as much as they could. Is this gangster behavior? I don't know. It looks more like the way states behave in the real world. Faced with threats or uncertainty governments assert themselves to ward off challengers.
What's irritating to some of us, is the way that some Rockwell libertarians portray government as a monster but make exceptions for the seceeding states or the Confederacy. They weren't lacking in those domineering and aggressive characteristics that are so objectionable in governments.
Unilateral secession will always be problematic because of the disagreement over the things the seceders can take with them. Of course the right of rebellion against tyranny exists. And those who favor separation are free to work peacefully towards that goal. But unilateral secession seems bound to produce wars, because each side will make itself the judge of the terms of separation.
Ex post facto legislation is unconstutional.
True, but I'm not really sure that term fits what Congress did in this case. Congress wasn't punishing anyone for things that were legal when they did them.