non sequitur
Wrong answer. Try again. Firing on Fort Sumter was every bit the aggressive action that claiming ownership of Fort Sumter by the north was. Which of these came first? Also, name ONE military installation not in the Confederacy that the South claimed part ownership of AFTER secession. One. Just ONE. There are always two sides to a story. Your side isn't being truthful to the facts.
Another point, did the South, after secession have a moral right to defend itself against northern aggression? Continuing to claim ownership of a fort no longer in your country is certainly an aggressive act. The South didn't do this to the north. They just wanted to be left alone to chart their own course. They had no intention of getting into a war with the north because they knew that they were at a severe disadvantage and would likely lose over the long run. The north wanted war and thus provoked it.