Well, sorry but I think he has a right to his opinion. He may be wrong in a lot of our books, but he gave reasons why he felt Johnson and Ledbetter were overrated. The point he makes about legend being an important element to greatness is well made. I do think some of the hero worship of RJ as The King of the Delta Blues gives influences like Son House rather short shrift. The criticism of Ledbetter as "AN AUTHENTIC NEGRO FROM THE SOUTH WHO WAS IN PRISON" walks the racism line, but I do think there is some accuracy to that point, enough to keep from crossing the line.
I think The Kingston Trio were about as faithful to the folk tradition as Faith Hill is to the country-western tradition and Celtic Woman to Irish Trad music. Nothing wrong with saying who you don't like...long as it aint everybody.