I am not aware of any racist Dems joining the Pubbies in the 60’s. There were some civil rights proponents who left the Dems and joined the Pubbies. The Dems did not take on the mantle of CR until Johnson made it a central part of his party’s platform. They vigorously opposed CR legislation up until then as we all know.
The Great Society was southern antebellum, allowing the Dems to keep the blacks segregated and control their vote.
Strom Thurmond for one.