We are professional pilots, we fly in different countries and the best way for everyone to understand each other, to have good SA is for everyone to speak a common language. That language is English, it could have been any other. That's why we have to have at least ICAO level 4 english. It has nothing to do with national pride. It is what was agree by all ICAO nations.
I'm Portuguese and in Portuguese airspace you hardly ever hear us speak in Portuguese, we speak in English, why don't the spanish and french do it too.