You should be there to train in the art of Aikido. If people want to play the game of trying to turn into a Japanese person, then by all means, allow them the space to do so. Heck, it can be quite amusing at times. You could even compliment them and let them know that the shape of their eyes is changing!
If the Aikido teaching is good, stick with what you are there for. If you do not believe that the Aikido instruction is good enough for you, look elsewhere.