What is so difficult to understand?
If there is a requirement for French language proficiency at certain small airports in France, it's only France complying with international standards. The reason for requiring language proficiency is to ensure that communications (usually) between ATC and pilots can be achieved without misunderstanding. Which is a good thing.
Claims that English is the 'international aviation language' are a misunderstanding of the rules. What ICAO says is
Aeroplane, airship, helicopter and powered-lift pilots and those flight navigators who are required to use the radio telephone aboard an aircraft shall demonstrate the ability to speak and understand the language used for radiotelephony communications.
The air-ground radiotelephony communications shall be conducted in the language normally used by the station on the ground or in the English language.
The English language shall be available, on request from any aircraft station, at all stations on the ground serving designated airports and routes used by international air services.
Put it all together and a small airport in any non-English speaking country can be designated as using the local language only. If that causes a problem then you will need to fly to an airport which is designated as having English communications available. Maybe rather than berating the French, we monolingual native English speakers should consider ourselves very, very lucky not to have to learn another language in order to fly internationally.
Pam fyddai unrhyw un eisiau hedfan i Abertawe beth bynnag?