Mark Twain said that when he was growing up in a slave state (Missouri) he was never confronted with a single dissenting viewpoint.
Pastors preached the (biblically erroneous) notion that Africans were cursed by God and therefore ought to be slaves.
No one saw any abuse of the slaves.
The slaves kept quiet about their opinion one way or the other.
In the Missouri of Twain’s youth slavery was a de facto good not evil.
A situation he addresses well in Huckleberry Finn.
But it was not true. Slavery was and is an abomination, an aggression against other humans.
What aggressions against humans do you take for granted or even passionately support?
Child sexual abuse?
Abortion is legal in the US and many people are passionately supportive of it. But it is a greater evil than slavery.
And while child abuse and human trafficking are illegal, if our government does not enforce their extinction, they will and do flourish in the gap.