Actually there was a huge shift during the civil rights era when racist/segregationists Democrats left that party initially to become Dixiecrats and then moved to the GOP where they were courted by the Southern Strategy.
The untold story of the ideological realignment that upended the nation
newrepublic.com
LBJ noted that after the Civil Rights and Voting Rights bills were passed that the Democratic Party would lose the South for a generation. He was right except it has been longer than a generation.
Those statues of Forrest and the cities, counties and schools named after him are in conservative Tennessee, which is a GOP stronghold. And it is the Republicans that have been resistant to removing those honors from Forrest, just as it is conservative Republicans who fly the Confederate flag and who celebrate the birthday of Robert E Lee on the birthday of MLK and who object to removal of statues that honor Confederate traitors and who object to voting rights for all.
This reconfiguration of the two parties has long been noticed by black people who now vote Dem.
The last KKK member of Congress was indeed a Dem who regretted his past association with the KKK and apologized.