The correct answer to this open question is the following.
To understand slavery in the South, we need to consider the economic value that slavery represented for the Confederated States.
The plantation system in the South -growing crops- was the most important economic activity in the region. So slaves were an important part to produce crops. Plantation owners depended on the work of slaves in the farm fields. Then, is not hard to understand why southern always opposed to the liberation of slaves. And of course, at the same time, that is why it really was very difficult for the Civil Rights movement to end racial discrimination and get equal rights protected by the United States Constitution.