just a few things come to mind...(it's early in morning, pre-coffee)
Leadbelly was (all together now)....a black man.
Writers usually compose about what is familiar to them.
MOST importantly, PC or no, as much as some of us would love to, history canNOT be rewritten as long as there are people alive who know, at least, some semblance of the truth. Hence...I believe songs have historical value. They teach how things were, they show us our progress (or lack thereof).
There are a lot of folk songs pertaining to topics that are "uncomfortable" but hopefully are no longer relevant except in an historical way. ie.-songs about Hitler and his unfortunate genetic accoutrements (sp?). Songs about country vs. country in the plight for freedom....songs about slavery....
I guess I could sum up my opinion by saying "lest we forget".