Because the average Democrat American doesn’t know squat about history, won’t listen to Republicans, doesn’t belive them, and the Democrats would turn around and say it isn’t true and add that it was the Republicans that are behind the KKK, Jim Crow, etc. The average RAT would believe that.
It is in the spirit of coexistence that Republicans say nothing about the Klan being the terrorist wing of the democrats.
Jim Crow(e) was one of the original Founding members of the Klan.