Battle Cry of Freedom

The South was concerned that the "Black Republican Party" was trying to allow the blacks to be able to own land and have whites be their slaves. The South was preaching that slavery was not bad. They praised all the benefits of being a slave. Why then were they so concerned?
They were trying to pretend that what they were doing was wonderful and for the betterment of the blacks. Did they really believe that?
When I read that the one slave that had found freedom and then after 20 years was being returned to her slave owner, was willing to slit the throat of her own daughter, so that she would not be subjected to slavery, I wondered how long the south could be blind to their own actions.