Good point.
Given LBJ's bigoted statements he made when he was trying to get the Civil Rights bill passed it is certainly possible and wouldn't surprise me.
That Johnson used words people used back then shouldn't surprise anybody, especially if he was using that language to make a point, but it would astound millions of people if the president who got civil rights legislation through Congress had been a KKK member.
Definitely. One would think there would be some way to find out conclusively if LBJ was in the KKK. It's not so much about exposing LBJ but further exposing the Democrat party.