Democratic southerners stopped being racist in 1944? Why do you think it took them so long after this date to become Republicans?
I didn't say that. I said that the national party started becoming unpalatable to Southerners after said date.
The reason it took so long for the South to vote Republican was long-term Civil War hostility; Southern Republicans were still seen as scalawags. It took a long time for that perception to go away, and the Democrats are still very strong in the Deep South (minus Georgia).