You can't please everybody. Because you sing a song about infanticide, doesn't mean you endorse it. The old ballads deal with a lot of uncomfortable subjects. I think a lot of our current problems stem from us sweeping these issues under the rug. I recall an article about Martin Carthy a few years ago in Folk Roots where he was discussing "Prince Heathen" and mentioned that it was not his job to do the audience's thinking for it. Also his liner notes on the same ballad recently said that he defied anyone to listen to the song and think that that was an OK way to behave. You should be able to sing what you want, if you want to preface the song with an introduction warning sensitive people, they can have the option of stepping out for a bathroom break.