I think “A Very Old Man With Enormous Wings” brings up some very interesting points and questions about human behavior — in particular, our inclination to trap all that is different and perhaps all that is beautiful. Throughout the story, the characters are incredibly fascinated by all that is out of the ordinary, but instead of admiring those differences, they are turned into something akin to sideshow horrors. In the case of the Angel, he is trapped with no choice of how he is seen or treated. I think this story provides an interesting commentary, perhaps unintentional, about how humans approach the unknown and unfamiliar.
I think it also provides a little insight into the behavior of religious people. One of the most interesting things about this story is how even though the people believe the man to be an angel, they still choose to trap him and use him for their own benefit. Although they believe him to be a messenger of the highest power, they abuse him just because he is weak and vulnerable. There is something– in my experience– so Catholic about claiming some part of God as your own, bending a part of the religion to fit exactly what you want it to be, ignoring every miracle, sign, and shred of evidence and focusing on your own idea of what your angel should be and look like. The story shows (of course to me) how malleable religion and beliefs can be.
I agree with what you said about how humans approach the unknown in many different ways. I think people often let their reactions to the unknown cloud their judgement of treatment of others.