Sounds like a misread of the teleprompter by the other affable Joe; Jen will need to circle back.
Otherwise, expect our beloved Brother Joe to once again heft the old burden - which has some controversial documentary support - that from the time of Lincoln's “house divided speech” the rail-splitter/nation-splitter had intentions to use the presidency and the military to violently overthrow constitutional slavery; because it was "all about freeing the slaves."
"Contraband of war" was well understood and practiced at least since the Revolutionary War -- i.e., Lord Dunmore's and Sir Clinton's proclamations.
In 1861 Unionists early-on understood that defeating the Confederacy could require destroying their power-base, slavery.
And arguably, Union anti-slavery actions were instrumental in driving many Southerners to support the Confederacy and its war efforts.
So, yes Virginia, when Jefferson Davis chose war at Fort Sumter, he chose a war against Confederates' "peculiar institution".