Is "Was Prot really an alien?" the real question about K-PAX movie?

I watched the movie many times, each time I changed my mind about the fact that Prot was really an alien or not. But after watching it one more time I became convinced that it doesn't matter and it is not the real question. If you want to believe he was an alien you are free to believe it I guess, but that doesn't matter. There are many references in the movie about real world characters and their messages to the humanity. I feel I'm near an answer but actually can't figure it out myself.

EDIT: Since downvotes, to downvoters:

1. Be open minded, feel free to downvote as long as you are constructive and apport content to the answer


2. Omg. It is not a duplicate.

"Was Prot really an alien?"

"Does really matters if Prot is an alien?"

Are 2 different questions.