The war was over slavery for the south.
The war was to put an end to the insurrection for the US government.
Where there was no insurrection, slavery was not affected by the EP, and absent an insurrection, the President had no power to end it.
Why not end it where they could? Most of the states not in insurrection had ended it where they could. The federal government had no authority to end slavery absent the insurrection, or absent a constitutional amendment.
If Abolition of Slavery is the Casus belli, and the overriding moral principle involved, than common sense would dictate that it should override every other consideration.
It didn't. Ergo, it was NOT the overriding moral principle involved.
As a matter of fact, Lincoln said he would keep slavery as long as the South would rejoin the Union.
Did you know that? Did you know that Lincoln was willing to KEEP slavery?
What's your next argument?