I think there are two different issues here.....

Traditional songs ( unless you are a purist) are fair game and have probably been changed many times already.
Modern songs(like "When all men sing") have been written by someone who is still alive and who should be consulted ( as a matter of courtesy ) before any changes are made.

As a woman I have no problems with the words of when all men sing - I do not believe it excludes women rather it encompasses them as part of " mankind ".But I would have problems if someone changed the words of my songs simply because THEY believed they were not politically correct. My reaction would be that if they don't like the song they don't have to sing it. Similarly, those who are offended by such lyrics don't have to listen.