Why did the skinned chickens fear the camera?
I was correct in my earlier comment - The skinned chickens don't want to be revealed to humankind so they avoid being photographed.

This is revealed in the first dialogue with the chickens:







If they knew of their existance, humanity could easily overpower them because of the chickens' feeble bodies. Hence they try to avoid the assistant.



Don't worry, the main character missed it too: