The Confederacy needed the munitions.The only reason it hasn't handed over Guantanamo is the fact that the USA can crush Cuba like a bug. If it didn't have that power, then Cuba could repossess it and It would be perfectly within its rights to do so. Anywhere else the host country wanted us to leave, we did. All you're arguing is that might makes right.
My point had nothing at all to do with "might makes right". As I wrote in my original post, South Carolina didn't own Fort Sumter when they attacked it. The fort belonged to the United States. South Carolina ceded the island it sits on to the United States on Dec 21, 1836 and thus the confederacy had no rightful claim to it. I equated that action to John Brown's raid on the federal armory in Harper's Ferry. Both attacked the United States and ended up paying the price.
You bring up the government should simply leave when asked. I responded with Guantanamo as example that the world doesn't operate that way. Another example would be the time it took for the United States to cede the Panama Canal back to Panama.