Hugo Black a liberal member of the KKK?

Hugo Black,a Associate Justice of Supreme Court from 1937 to 1971.When Franklin D. Roosevelt(FDR) nominated Hugo Black to the Supreme Court eyebrow were raised when it was learned he had been a member of the Ku Klux Klan(KKK).It might surprise people that in U.S Senate Black was firebrand liberal,although maybe populist would be more apropos.Many Southern politicians raved against Black people, Jews but also big corporation,indeed,Black name his name in Senate by destroying William Boeing,who not only founded the Boeing corp. but, in a way,was father of aviation industry,for example he introduced many novelties to airlines(he started what would later become United Airlines)included having two pilots,flying at night,stewardess and two way radio telephones.So what was his big crime? He made money,he was successful and although he was cleared of wrongdoing,seven years after Black started his investigation Boeing couldn't take the spotlight and people like Black saying he wasn't patriotic for was very much an American hero,but sold his stock in Boeing and went quietly into that good night.
Black always stated FDR didn't know he was member of Klan,however,on his death bed he admitted he told FDR who said,don't worry about it,I have lots of friend in that organization.Black was a big liberal on the bench and strong supporter of Civil Rights.