Your history is wrong GfS.
Many Democrats left to become Republicans in the 1950s and 1960s because they opposed the Civil Rights movement.
Bobert is talking about 1979. Yes, the "Reagan Democrats" also switched over in 1980, but the Democrats who were "vastly pro-segregationist" were already Republicans in 1979.
The South is not slow-learning. Many feel that they have nothing to learn.