Stephen Hawking is terrified of our first contact with aliens, especially if they come here. He explains it for the discovery channel, here:
The takeaway from that video: Remember when Europe landed in the “Americas” and it ended really poorly for the indigenous population? If intelligent life makes it to us, Hawking predicts the same scenario. If these Aliens are spending all these resources going across the universe from their planet to ours, it probably isn’t to say “hello.” They want our oceans and possibly our organs. Hawking’s scenario isn’t Zephryn Cochran meets the Vulcans, it’s War of the Worlds.
So let’s call that the worst case scenario. The best case scenario is space gnosis, which I’ll discuss in act three. But what about a more neutral scenario? The aliens neither want to kill us nor bring world peace, they just sort of are.
There’s this notion that in the face of Aliens, a new intelligent “other” to our entire species, the humans will all suddenly get along. It’ll be the end of the nation state and the birth of the “planet state.” I guess that doesn’t seem totally out of the question. But I’m not convinced. What, there’s a civilization on Ceres so suddenly geographical, racial, ethnic, sexual, economical, and historical differences on earth don’t matter? That might happen in time, but humans have a lot of infighting to get through first. I think we’ll be unpleasantly surprised to discover the human ability to harbor prejudice against aliens and other humans at the same time. In fact Hawking]s worst case scenario would probably be a much better unifying force provided no country manages to barter a treaty with the invaders.
I’m interested to see how our various religions handle the news of intelligent life. My home faith, Mormonism, is actually surprisingly well equipped for this. Deep LDS doctrine has long held that God (well Jesus as Jehovah) made other planets with people on them. Other Christianities will have to debate how the whole “qui tollis peccata mundi” thing will work in the face of a populated macrocosmica. Deep doctrine Mormonism already believes that Christ’s “atonement” covered the whole universe, but that he had to die on earth because we were the only planet wicked enough to crucify our god.
Then there’s the Biblical literalists, that is: people who believe the earth was literally made in seven days, that Adam and Eve literally existed, that Jonah was literally swallowed by a “great fish” and so on. This line of thought will have a hard time surviving the discovery of aliens. Aliens simply aren’t in the bible. Some might insist that what we’re now calling aliens were once called angels or Sepharim. But that theory won’t hold on once these aliens prove they’re definitely not the heavenly host of YHWH, or Elohim, or even Metatron. Others might say that there are no aliens in the Bible because it wasn’t important to mention. It’s a good answer, but it’s sort of a non-answer. Non-answers don’t keep people in pews.
Up and coming scholar of Hinduism, Scott Lynn Brown, informs me that Hindus and Buddhists have long believed in an infinite number or worlds with an infinite number of beings on them, so an alien visit shouldn’t send too many shockwaves through their more formal theologies. The visit would just reopen questions on whether being reborn on a different planet is possible, and if it would be a higher rebirth (almost god like), a lower rebirth (because you’re denied the possibility to learn Hindu or Buddhist Dharma) or just an equivalent rebirth.
Ultimately, I do think finding other intelligent life in the universe will be a game changer. It will have to change how humans conceive of ourselves as a species. It will give us a new mirror to view ourselves But we have flaws, we fear change. Let’s not over exaggerate how quick or drastic this transformation will be.
 I should stress people as in humans. If they’re too far from Humanoid, Mormonism won’t really know what to do.