This subject comes back every year on PPrune, and inevitably comes down to French on the frequency,and ends up in "them against us" .
And every year I come up here to tell the same simple things :
Bad, wrong or lack of using standard Phraseology has killed, and will kill far,far more than dual language use.
Yes a single language would be great , like peace on earth and a single loving religion for everyone.
In absence of that stick to Standard ICAO phraseology , best thing so far.
Last thing : for info , in CDG, it is not the controllers that object to English only ( most would prefer that ) but it is Air France Pilots unions...but with AF current situation, the problem might solve itself .. ( bad joke unfortunately )