Re changing the lyric to suit yourself = If its a composed song , melody AND Lyric , and you want to alter the words its only polite to ask the writer if he has any objection ! And , of course , credit the original writer when you perform the song !

With Traditional material , and Public domain , this is not a matter of great import , of course , but I am quite happy with Traditional songs that are about subjects that I am not happy with - Whaling , Hunting , etc , as long as they ARE good songs that an Audience can appreciate and join in the chorus .