Little attention is paid to Forrest and if this be true his biography is just a slanderous attack. He might have been more slandered than Alexander Hamilton.
How did the KKK klaim originate? It claims he was a founder but resigned after a year or so.
The KKK claim.....there's no evidence he was in it. His actions and public utterances go against the idea that he was actually in it. When disbanding his troops at the end of the war he told them to obey the law and he took public positions in favor of admitting Blacks to all the professions, no discrimination, etc. He denied he was in it in his congressional testimony. Its almost certain recruiters for the KKK used his name in order to recruit and spread word that he supported it. He was a famous war hero in Tennessee after all. That's probably where the accusations come from. We have to remember that the KKK at that time....ie during the Occupation....was not the same as the 20th century reincarnation of it. It was lawless. It could certainly be violent. It was certainly racist. Then again it was fighting against occupation governments that were manifestly corrupt, governments which levied ruinous taxes on people and dispossessed people of their homes for inability to pay those taxes and governments in which corrupt carpet baggers then stole the tax money and the land. Remember too that almost all of the voters in the South had been disenfranchised during the Occupation so this was massive taxation without representation. It should not surprise anybody that there would be violent opposition to this. So both the Occupation governments and the KKK were quite dirty here.