"Will they make them sing in German, even the piegons?" Explain

This is a rhetorical question asked by Franz when orders were received from Berlin to stop the teaching of French in Alsace and Lorraine. The question conveys the dictatorial attitude and desire for power that makes man want to rule over not just political and geographical  territory but also over the minds of the ruled.Franz wonders at some domination where man tries to enslave the minds of people by compelling them to speak in their language. Franz feels that such a desire is irrational & unjust since it conveys a wish to master the forces of nature.The question raised by Franz is very pertinent/relevant.
He in his innocent imagination wonders whether it is really possible to enslave the minds of people. He is sarcastic towards and critical of the attitude of the Germans. Pigeons are a symbol of nature.Franz indicates that just as it is impossible to enslave the spirit of pigeons and take away their right to coo naturally,similarly no one can take away the right of the French people to think and speak in their own language. The theme of linguistic chauvinism is brought out through this question.