Regarding the whole issue of altering lyrics to be more politically sensitive: Societies have a tendency to try to cover up things that make people uncomfortable. If we do enough of this, eventually all the mistakes will just "disappear" like they never happened. Years from now, somebody will claim that no person with dark skin and hair was ever referred to as "nigger", because if they had, there would surely be examples in the songs of that day.
An explanation of the use of derogative terms is definitely needed in performances. Also perhaps a mention that the terms did not have the same name-calling power that they have today. I believe the "n" word (I'm not typing it twice) was commonly (if insensitively) used without hostility (but with obvious disrespect).
Hopefully, society will some day look upon racism as a strange, terrible, inexplicable part of our past.
Jeri