I would attack someone who wouldn't leave my property too. But the truth is that the action was provoked by U.S. President James Buchanan and then Lincoln attempting to add more guns and resupply the fort. Also remember that not a single soldier died in the battles.
If Lincoln had withdrawn from Sumter and not launched headlong into a war there wouldn't have been 660,000 deaths. All the casualties and the later abuses of power fall squarely on Lincoln's shoulders.
That’s exactly how the union felt, considering that Sumter was their property.
You could just as easily say that if Davis had not fired on Sumter then all those deaths could have been avoided. What threat was Sumter to the South, even had Lincoln been able to resupply the fort? Did it threaten the safety of the Confederacy? No, Charleston was one port and besides, the troops in the port had done nothing to interfere with shipping into and out of Charleston. Did the troops there take any hostile action aganst Confederate forces? No, they stood their post and didn't fire at anything. So why the attack? The only purpose for firing on Sumter was to provoke a conflict. One has to ask why Davis chose to do so if he didn't want a war with the North.
“I would attack someone who wouldn’t leave my property too”
Something that always irks me about “first shot” arguments is that they are taken to mean whoever is responsible deserves what they get. But not all casus belli are created equal. You are allowed to fight for recompense for stolen or damaged goods, and also to punish wrongdoing. But of course conquering and forcing submission under the Constitution forevermore is not just punishment for Ft. Sumter.
It wasn’t meant to be, anyway. The Civil War was fought on the pretext that the Confederacy was a conspiracy of treason against the just laws of the federal government, and that all participants and sympathizers were insurrectionists. Ft. Sumter was merely a symbol for the pretended that the North was in some kind of danger. Which is a lie. The blessed union was in danger, but not whatever would have been left of the union had the South gone in peace.
It wasn’t rebel property. The fort was built on a shoal, by the United States. The shoal had never been part of South Carolina land.