I do take your point.  I'm not really trying to be proscriptive, and I imagine that the majority of people here would disagree with me in any case, so it's just my personal opinion.  I do feel, though, that there has been rather of lot of what almost amounts to cultural imperialism in the Folk Revival; "cherry picking", if you like, of interesting pieces from other languages and cultures, all too rarely accompanied by any real attempt to understand the context from which they arose, or what the words actually mean.  It seems to me disrespectful of others' cultures to demand that kind of instant gratification; "It's only a song", or, "I'll do what I want and nobody has the right to criticise me" are common reactions, but they beg the question.

Of course, song is a very good vehicle for teaching languages; I learnt a good few French songs at school as part of that process, including the one you mention, though we always sang that in tandem with a translation.  I still sing French songs from time to time, but only because I mastered the language and know exactly what I'm doing.  Though I would love to sing in Gaelic, too, I know only too well that it would be little better than a parody given my very slight grasp of the language, so I leave it well alone.  That's a personal choice, but I do think it's the right one.

Malcolm