I should say something here, because I'm afraid I can sound very black & white, right & wrong about things sometimes. I'm not.I suppose I have a double standard. I AM fatalistic about my own songs. The most fatalistic belief I could hold is that no one will sing them other than me. That's fine - if I wrote them for any other reason than I loved writing them, I never would have bothered.
I will berate myself for making minor mistakes and completely miss other people making them. I would miss changes to songs I'd written because I'd probably be too excited that they even cared enough to sing them. When I learn other people's songs, I do my best to learn their words and tune although I'll sing it my own way. When I hear other people take liberties with the songs of others, it bugs me. Not the mistakes, but what seems like a deliberate change. There are songs I don't sing because one line drives me nuts. I'm capable or re-writing it, but I don't feel I have the right. Plus, if enough people know the song, it would be pretty obvious to them I messed with it. I just don't sing it.