Again, I don’t remember any straight-up minstrel shows performed for the general public in the 1960s, and I was all over the South in that period, but I’ll just have to take your word for it.
There is a documentation of their taking place, if you don’t want to take my word for it. Do a google search of blackface or minstrel shows. These reports match my recollections very well. http://en.wikipedia.org/wiki/Minstrel_show
http://en.wikipedia.org/wiki/Blackface
I never said they were in the South. I remember them up north from the theater circuit and on broadcast TV shows.
General public performances in the US trailed off at the end of the 1960s, but certainly private shows went on for another decade. The All in the Family program in the 70s was making a social comment on the fact that these minstrel shows still existed.