I'm sure all those Democrats who signed the Manifesto - including such notables as LBJ, Gore Sr, Fulbright, Wright, and Rayburn - did so not because they were racists, but because they were true strict Constitutionalists who believed in the 10th Amendment and states' rights.
/s
Also, Wright and Rayburn did not sign.
The only one on your list who did was Slick Willy’s mentor.