I think it's a matter of developing a sensitivity toward what an audience can or cannot appreciate. Is it appropriate to sing " Grandma Got Run Over by a Reindeer" at a Christmas performance in a nursing home? I think it is, and I have sung of a verse or two of the song at nursing home performances on occasion. However, some of my fellow performers were not happy with me for singing it.
In singing to an audience of Folk Music enthusiasts, I do not think I need to be overly careful about singing songs that come from history that have elements that might not be understood by a general audience. I do not think that the rules are the same for every audience. It is a matter of adjusting to the sensitivities of particular audiences. I think that as a performer, my primary obligation is to my audience.
Joe