I can understand the sentiments of covec there does seem to be a massive door slammed in an english speaking only persons face if they do not have another language to icao level 4 equivalent for a non uk european carrier.
To be honest it would be far wiser for an airline to be sensible and invite people whether the person knows the language of the carrier i.e. German or French and ask the pilot if on the offer of a job would they be willing to learn the language of the country in their own time. I am sure most would jump at the chance this should be the win win scenario.
As for English currently used this goes all the way back to ICAO and the decision was made at that and pointless to discuss it. There are countries which do not bother with this such as China where plenty of chat with ATC is in the native language and to be frank if they are talking level 4 English we might as well all give up.
I have heard of ways people manipulate a system floor to make it look like they have level 4 english at a good standard and reality is they cannot converse properly. I have personally met someone from a European nation during a training course and to be honest I spent more time trying to confirm what was been said.
As for discrimination I have never seen an industry which is riddled with so many undercover forms of discrimination with Eastern European carriers preferring not to take Western Europeans .... Also there seems to be a ridiculous impression that people over 40 are finished and not worthy of an interview... then comes the discrimination due to the sex of a person ...
No common sense is been used by airlines