Ah, but Christy Moore recorded it, and people think Christy shites marmalade, therefore it can't be a bad song.
Mary, you did the professional thing to do.
If someone hires you and requests a particular song, do it to the best of your ability - which you did- and to hell with the begrudgers.
You wouldn't believe some of the stuff I've had to learn for weddings (and funerals too).
Seamus