While not quite directly related to German language teachers in World War 1 or the Western world, Leon Trotsky does describe something similar is Tsarist Russia. In his autobiography, My Life, Trotsky talks about how nationalist and anti-German sentiments under Czar Alexander led to a noticeable marginalisation of German language teachers during his childhood.

I would suspect that similar sentiments and attitudes existed during World War 1 in the Western World.