Wasn't it the Liberals that wanted to Keep slavery going ??
You mean the Democratic Party. There are both republican and democrats who are liberal thinking people.
Southern democrats opposed the civil rights movement until the mid-twentieth century when there was dramatic ideological shift in the Democratic party that occurred in the mid-20th century or around 1933 when President Franklin New Deal was launched.
Southern plantation owners relied on slavery to cultivate cash crops like tobacco and cotton, maximizing profits by minimizing labor costs. Understandably, they were not excited to see this come to an end. Today, the farming industry relies on low-paid immigrants (legal and illegal) to harvest their crops.