See my response in #33 on this thread.
True. We don’t know if true or not true... until we hear the audio recordings and see the photographs, which allegedly exist.
Whatever this country wishes were true about the progress made by the Civil Rights Movement, the Negro/black/Afro-American/African-American population back then was overall exponentially better off then it is now. I was alive then. There is no comparison. Johnson's Great Society programs of Medicare and the War on Poverty caused the death of the greatest medical system in the world and the rising black middle class.
There is nothing surprising thus reported about MLK. Joan Baez was one of the top folk singers in the U.S. Part of the free love generation, part of its in-crowd. She was also part of the Communist movement, like Pete Seeger. She'd see MLK as a heroic figure and he'd probably see her as what she was: a famous, successful, attractive, white fellow-traveler.