Why do we always think the worst of aliens when they arrive planetside and start talking about peace? There are plenty of alien groups who exist only to make the world a better place. No, really!
I realize that half the time when an alien says "We come in peace," they really mean something like "We come to impregnate your men and cover your entire planet in red vines and poisonous gas." But occasionally these aliens really have our best interests at heart. Even if they have a funny way of showing it. Here's a list of the most helpful aliens who ever visited Earth.
Sometimes the aliens are like the little guy from E.T. The Extraterrestrial, and they aren't exactly coming to bring us goodies - but they think we're pretty nice and just want to sample some of our flowers and stuff. Sometimes, if they look snacky like Jeff Bridges did in Starman (which features a nice long shot of his naked alien bum), they might have sex with some humans while they're here. Which is also friendly of them. We're not sure what the aliens in Close Encounters of the Third Kind have in mind for Richard Dreyfuss at the end of the flick, but anybody who has seen Communion might have a few ideas.
Like the aliens in Close Encounters, the space creatures in Knowing seem like bad guys until the end of the movie, when they are revealed as our best pals who are just trying to help out. Come to think of it, this is sort of the idea in the original The Day the Earth Stood Still (though more so in the remake). Sometimes a light-filled being who has lots of wisdom needs to show tough love. Especially if they're going to convince us not to nuke each other and destroy the planet.
And then there are the aliens who stop by just to say they love us. Such is the case in Contact, where aliens send us a message about how to build a giant piece of technology that's basically just a kind of virtual reality telephone system that shows Jody Foster some beautiful space vistas and reminds her that her dead dad loved her. Awww, thanks, alien peoples! But how about some clean energy and spaceships too?
K-PAX is another flick in this genre, though we're never sure if Kevin Spacey really is an alien or just a crazy guy who wants to make us all feel better about ourselves.
Other aliens are hellbent on changing us so that they can have a nicer relationship with us. We see that in Octavia Butler's Lilith's Brood trilogy, where tentacle-covered aliens rescue the survivors of a nuke apocalypse and then set about genetically engineering some hybrid babies with them. And in Ken MacLeod's Engines of Light trilogy, we meet up with alien creatures who transform human culture by moving some of us halfway across the universe and then crawling up inside our noses and making us virtually immortal. OK, so I'm reducing a lot of thematic complexities here but essentially that's what happens.
I think my favorite benevolent alien invasion series is L. Timmel Duchamp's Marq'ssan Cycle, where the aliens are these hyper-democratic, anti-violence feminists who constantly argue with each other about how they can change human culture for the better without oppressing us. I love the idea that aliens would be arguing over how to reshape Earth culture like academics at a sociology meeting. It's not too far removed from what we learn about the Vulcans in the Star Trek series: They too come to Earth to make first contact and help us out, but there is a lot of division in their ranks over how this intervention should be accomplished and whether humanity even deserves it. Unfortunately, some aliens who want to help us have a rough time because they're just not appealing to mainstream media. That's where John Scalzi's Agent to the Stars comes in. He'll help sell the aliens' message of peace to the media-guzzling masses.
Even more fun are the aliens like Doctor Who and the universe-hoppers in Iain M. Banks' Transition, who are completely open about the fact that they want to change Earth culture for the better. There's no ambiguity or "gee should we really impose our will?" The Doctor, though he's generally a very thoughtful guy, is also quite happy to stick his nose into any situation and screw the idea of a "prime directive" or fears of cultural imperialism. There's a right way to do things, and it has to do with science and rationality and compassion. And dammit, the Doctor is going to force it on you! Though we're never quite sure whether the people in Transition have humanity's best interests at heart, certainly some of the characters do - they are actively trying to foster democracy and undermine tyranny on every alternate Earth they can find.
My point is that even when an alien waves a giant robot at you, or sucks your kid out the doggie door, it may actually be trying to help. Also, if the alien looks like Jeff Bridges circa 1980s, you should definitely have sex with it. Oh yeah, and peace is great and please try to keep the planet green and all that stuff too!