>Non-violence is effective as an alternative to violence.

I have a feeling you probably should have put a bunch of caveats for both like "if you're willing to wait a few generations for your aims to be met".

When talking about both the American civil war, one side had engaged in violence for antiquity and had the force of the state which came to state that violence was the expected behavior. This violent behavior was very profitable, and the people profiting from this realize they were in a weak position so they started propagandizing was what they were doing was "in the name of god", "is good for the common man", etc. It moves the conversation from one looking at the violence of slavery to "Why do you hate god and country".

Simply put the US civil war was a temporary increase of violence that preceded the war with slavery and followed the war in neo-slavery.