I beleive this language issue to be quite easy really.
French controlers and many of those who are writting are wrong.
Its this simple: Speak the language you wish. UNLESS the situation dictates the need for others to understand what is going on, for instance, LVP procedures in force, climbing/descending through other levels were other aircraft not speaking your native language are involved.... Donīt you agree?
So, it is not necessary to always speak in English, nor in your native language, you just have to use the brains god gave you and know when to use which. Its that simple and there is no argument to this.
By the way, for those who beleive English should be used at all times, make these considerations:
No.1, Try to imagine English was not your mother language (its very easy to discuss this when it is)
No.2, English is not the most used language througout the world. It is beaten by Chinese and Spanish (English is third in the list iīm affraid). So consider yourselves to be very lucky when English appears to be the common language.
No.3, English is not the only language considerd by ICAO.
No.4, The common language (English) is to be used ONLY when it is considered that other traffic need to know what is going on. (I deeply agree with this because it is the last barrier we have in order to block off accidents/incidents/frights...etc), but ONLY in this scenario, not always as many would like.
This is just my opinion.