When [Nathan Bedford Forrest] took over leadership of the Klan in 1867, it represented the guerrilla continuation of the war he had tried to fight as a Confederate General. In essence he exchanged his Confederate grey for a white sheet. The earliest Klan, then, was a restorationist movement of the Confederacy.
The Invisible Empire was something quite different when it arose in the 1920s. It was essentially a bourgeois, nativist movement. [..] It was a right wing, white supremacist, but essentially mainstream bourgeois movement. That is, it intended to control, through the traditional political legal apparatus, the politics of the United States government and as many state and local governments as possible.
When the Klan was resurgent in the 1960s, it was essentially a backward-looking movement attempting to preserve what was most reactionary and most peculiar of the institutions of the segregated white South. It was under that banner, represented everywhere by the battle flag of the Confederacy, that it went out and did its beatings, bombings, lynchings, mutilations, and castrations.
It is something quite different today.