“The side flying the old glory fought a civil war to abolish slavery. “
No, they didn’t. You need to read history and stop looking at it as it was told to you in the 3rd grade.
Since you don’t know history, Lincoln never freed the slaves.
It hardly matters what the “real” reason for starting civil war was. What ALWAYS matters in life is the RESULT. And the result of Union army winning was end of slavery in United States.