Crap. The Union had legal slavery. It was protected by the US Constitution. The Flag of Slavery was the flag of the USA.
Slavery was an *AFTER THE FACT* excuse to justify the bloodshed Lincoln launched to stop European trade from moving to the South and out of the Control of Washington DC.
You keep banging the drum of "evil system of human bondage" because the real facts don't fit your compelling need to justify the invasion and subjugation of people who wanted independence.
You force it to be about slavery, because you dare not accept it was about Independence. It wasn't about slavery when it began. It wasn't about slavery for the entire first year of the conflict.
It didn't become about slavery until January of 1863. It wasn't even about slavery then, because Union slave states were still holding people in "an evil system of human bondage." Except it wasn't so evil when they were doing it. In fact, Union states were holding people in "an evil system of human bondage" for 8 months longer than those evil Southerners.
It was about RAW POWER and CONTROL of money. 200 million dollars in European money that was about to be yanked from New York. That is what the war was about.
It looks like you are up against the usual virtue-signallers who refuse to see that there could be several complex and nuanced reasons for why the war occurred. It’s more important to show off about how they are against slavery - as if that’s taking some revolutionary bad-ass position, lol!
Tell me stupid. Where in The Constitution is the clause allowing slavery?