The meaning of the murals could be easily interpreted as a pacifist’s message; in a simple sense, that war and genocide leads to misery and the end of peace, but through finding peace and dismantling the machine of war the world can become paradise.
The tunnels at the airport seem fishy, but why would you set up a concentration camp at an airport? I suspect the real reason for their existence would be for something related to the fact that this is one of the airport hubs of North America; and the most likely choice would be to store supplies that might potentially need to be transported on short notice (potentially for disaster relief). If this was a government program, this could be seen as vital infrastructure which would explain why it was kept secret.
