Slavery was legal in the Union. You are trying to measure the conditions of that time by modern ideas of morality. The Union did not fight the war to abolish slavery. They fought that war to stop Independence for Southern states.
We want to be free to enslave our fellow man!
Which they would also have been allowed to do as members of the Union. Indeed, there were five Union States in which Slavery continued all throughout the Civil War.
Actually, I'm measuring it by the worries and concerns of the Southern states when it comes to what they thought Lincoln would do if he became President.
I'm aware of Lincoln's statements about preserving the Union whether or not he could end slavery.
What doesn't get as much air time is the Southern states insistence that Lincoln not allow slavery in the new states as they were admitted to the Union. No ifs, ands or buts about it. And THAT is why they seceded.
That is simply inarguable.
You know better than that, Di.
When the war ended, there were only two states where slavery remained legal. DE and KY. Slave in all other states had already been freed either by the Emancipation Proclamation or by state action.