I think is they right to do so and many other things to protect their interest.
Many european countries requests that you must speak their languages (Germany, France...) or to be a citizen to work.
Let the turkish do whatever they want to...somebody will accept the rules, others won't and life goes on anyway.
AMEN !!
why do they have so much yabancie pilots - because they do not have enough qualified turkish pilots
and even with the dgca plans they will not get enough enough QUALIFIED turkish pilots
aviaition is years behind
and just to add: I prefer to work with a young yabanci pilot, instead of an high-godlike-overqualified-overexperienced turkish pilot - you know why ? they are motivated, well educated and have CRM and already airmanship. something you do not find with local pilots - hardly.