Take a look at the entertainment
Terran children are bombarded with -- your
cartoons, movies, comic books, television shows, and video games.
Extraterrestrials, portrayed as
monsters, are continually being killed by
humans attempting to save
Earth or a Terran ship. Although the aliens are sometimes very
technologically advanced, they inexplicably use this knowledge for
evil, such as conquering planets, eradicating
species, or infesting minds and bodies like a
parasite. In the end, like any
movie monster, they are always killed, usually to audience cheers and
rousing music. No other group of individuals is as universally
hated or
feared as aliens in human
media. From the time of
birth, humans are trained to fear
outsiders, and to destroy them with
no remorse. Is it too difficult for
humankind to realize that there are no such thing as
enemies?
Other pop culture extraterrestrials are cold and heartless, conducting disturbing scientific experiments and impregnating human women. When they have feelings, they are exploited for comic effect, like E.T. or ALF. They are devoid of clothes, styles, or any sense of individuality. They are machines, or poorly written plot devices. They are freaks, murderers, and monsters.
The suggestion that the barbaric and primitive human race is a higher moral creature than a technologically advanced spacefaring community is patently absurd. In this universe, continual warfare and ecological ignorance tend to wipe out belligerent aliens while still at the current human level of development. It's no surprise that this very race teeters on extinction. Now is the time of the choice between fear and strength, between the way of the Luciferians and the way of Ti and Do, the UFO Two. Those prepared for interstellar travel will move on; the remainder will enact a slow yet deliberate suicide. The biggest threats to humanity exist on the surface of the planet itself.
XCom, and games like it, are manifestations of a very dangerous and unfounded fear of the unknown.