The CSA was a separatist movement not a conquering nation hell bent on subduing the USA. What a crock. You are really twisted.
Sorry, but you have it all wrong.
In early 1861, the CSA was indeed hell bent on subduing the USA -- splitting it apart, taking border states & territories at will, seizing Federal properties, threatening government officials, firing on Union ships.
For example, Confederates' assault on Fort Sumter was as much an act of war as was the Japanese attack on Pearl Harbor.
But in case there was any doubt, the Confederacy soon formally declared war and increased its army from 100,000 to 500,000.
This at a time when the US Army still totaled around 17,000.
So there is no doubt -- none, nada -- in 1861 the Confederacy was a "hell bent" existential threat which President Lincoln was duty-bound to oppose and defeat.
It's that simple.