We obviously have different opinions. When a state took property owned by its deputy, the United States government, for the future safety of the state's people, I think it was a different matter. Or at least it was back then. If the states were going out of the Union in a few days or weeks, which they were, then the matter of when they took possession of property in the name of the state is almost immaterial. If it were "rebellion, insurrection or domestic violence" as you say, why didn't the federal government rise up at that point and invade the South. The feds didn't have the public behind them at that point. If the states hadn't gone ahead with secession I suspect the seized forts, etc., would have been returned to the federal government. The Arkansas arsenal was taken by the governor in the name of the United States, for example.
We are talking about a different point in time here back when states were the check against the power of the central government and vice versa. Secession was thought permissible by many, if not most, people like the New York ratification document I posted said. Indeed, several attempts were made by Northern Republican congressmen in early 1861 to pass an amendment outlawing secession or requiring all states to approve the withdrawal of a state. If it was already illegal, why were amendments proposed to outlaw it? Why would states ever agree to such an amendment that left them at the mercy of other states that might be taking advantage of them in some way?
Anderson sent the following in a note to his superior on December 28, 1860. It shows that Fort Moultrie was then held under the authority of the sovereign state of South Carolina.
I sent my post adjutant this morning with a message to the commanding officer of Fort Moultrie asking by what authority he held possession of that work, and desiring to know whether he would make any opposition to my sending for some property, public and private, left there. He replied to my first question that he held that post by authority of the sovereign State of South Carolina, and in obedience to the orders of the governor.
South Carolina and later the Confederate government both offered to negotiate about the forts, the public debt, etc., but were rebuffed. The South came out on the short end of the stick in value because by seceding they left behind their share of the Northern forts and government buildings and their share of land in the territories. Territorial land was worth billions at that point in time, and it far far outweighed in value any forts or armories taken by the South.
Again, we are talking about the short period, from Lincoln's election in November 1860 to his inauguration in March 1861. During that time everyone in the North, including Buchanan and Lincoln were trying to think of ways to satisfy Southern demands.
In the South, what was going on was:
In response, Buchanan made no efforts to defend any of these properties, except Fort Sumter and in Pensacola, Florida, Fort Pickens. The defense of Fort Pickens was successful, btw.
Soon after taking office, President Lincoln began preparations for a second attempt at defending Fort Sumter.
Bottom line: none of the constitutional arguments about "states rights" can justify illegal seizures of Federal property BEFORE secession. Even AFTER declaring secession, the legal course would have been to negotiate settlement terms. This is just what the US spent YEARS doing with Great Britain after the Revolutionary War. Instead, after just a few WEEKS, Southern delegates got mad, went home and started shooting at northerners.
The result was war.