I am thinking you are underestimating Christians, tho' I do admit that there are some sects that refuse to accept that man landed on the moon and there would be some sects claiming alien beings to be demonic at first, (and even some who would insist upon it even after several years passed by, afterall, some people are so willing to believe in conspiracies, theyjust can't help themselves, and some would always doubt the aliens) (btw- I tend to be an agnostic, so I am not defending myself religious beliefs that statement.)
However, what happens IF some Little Grren Dudes land and don't pray 5 times a day while bowing towards Mecca? Now, not all memebers of a group are identicle, but what would be the reaction of Islamic fundamentalists?