Chiennes de Garde say they do not want an equivalent to the English Ms but the use of madame for women of all ages, married or not.It's funny how these things shake out. The texture of language and culture is subtle. There's no objective answer to what is sexist and anti-sexist; these things play out in highly specific context.
Whether the guardians of the French language, the Academie Francaise, will accept that is another matter.
It still insists that female cabinet ministers are referred to by the male le as in Madame Le Ministre.
Perhaps, then, this issue will have to wait until France has a Madame le President?
It's tempting to think that we're ahead of the curve on the French on this one. Sort of. Newspapers and government documents and so forth in the US generally use Ms ... but if you fill out a form to rent an apartment, you'll probably be offered check boxes for Mr, Mrs, Miss, and Ms, to cover all of the bases. American feminism has come to a place where a commitment the rhetoric of personal choice—itself tangled up in distinctly American ideas of individualism and independance—demands that we respect the preferences of women who are uncomfortable with "Ms," even if we believe that this preference supports sexism and patriarchy.
And that "Madame le President" bit tickles me. Honestly, my first thought is of Battlestar Galactica, where crewmembers refer to officers, male or female, as "sir." It's a little science fiction gimmick which tells you that there's a kind of gender egalitarianism in their society which is somehow subtly different from what we have in our own.
Which brings me back to how I said that it's tempting to think that we're "ahead of the curve." But consider: we all know, somehow, that when a woman is finally elected President of the United States, we will address her as "Madame President." But how odd that we've quietly agreed on this issue when we still appear to be miles away from actually electing a woman to the job, when Pakistan had a woman as Prime Minister almost twenty years ago—and that's a country where many women are wearing burqas, which we think of as a kind of sign of Infinite Sexism. Which is, of course, a vast oversimplification.