Sorry, FRiend, but facts are facts and as John Adams, Ronald Reagan and others have noted: "facts are stubborn things."
The fact is that Fort Sumter was only one of dozens of Federally owned facilities unlawfully seized by secessionists in January through April, 1861.
Some were seized even before a state formally declared secession, and so are obvious cases of rebellion and insurrection.
Regardless, there's no law anywhere which says that US government property suddenly, magically, becomes not US property just because somebody declares it so.
In fact, when some self-proclaimed "government" begins seizing US property, threatening and attacking US officials, those are each acts of rebellion, insurrection and/or war.
Both Presidents Buchanan and Lincoln attempted to peacefully resupply US troops in Fort Sumter and both were defeated by secessionist gun-fire -- acts of war on the United States.
Lincoln's attempt further resulted in a Confederate military assault on Sumter, causing its surrender.
So blaming Lincoln for Confederates' assault on Fort Sumter is like blaming President Franklin Roosevelt for the Japanese attack on Pearl Harbor -- certainly there were things each might have done differently.
But the bottom line is: both attacks started wars which resulted in the Unconditional Surrender of the military force which assaulted the United States.
Maybe a better comparative analogy would blaming Lincoln for Confederates' assault on Fort Sumter is like blaming President Johnson for the North Vietnamese firing on the Turner Joy...