One of the reasons terms like "illegal alien" and "illegal immigrant" and their shortened version, "illegals," are so noxious is that, as I've discussed, it's such clear form of dehumanization. And once it gains ready circulation, it becomes a reflexive thing.
So much so that, nowadays, you'll find half-thinking media nabobs calling Latinos living in their own country "illegals."
Exhibit A: Wonkette last week:
We cannot write a better introduction than this: "A town in South America is living in fear after several sightings of a 'creepy gnome' that locals claim stalks the streets at night. The midget -- which wears a pointy hat and has a distinctive sideways walk -- was caught on video last week by a terrified group of youngsters." This sidling wicket goblin, who is terrorizing Argentinian Mexicans, made one teenager "so scared after seeing that thing that we had to take him to the hospital."
Hmm... a hobbit gnome terrorizing illegals? This is no mystery at all.
You have to wonder if Wonkette has ever even looked at a map of Latin America -- because, you know, that might help her to understand that Argentina and Mexico are a long ways away from each other.
But you have to wonder about the intellectual capacity of anyone who would refer to villagers in their native land as "illegals."
UPDATE: Several commenters have pointed out that Wonkette is a satirical site, and of course, it's obvious that the post was intended to be satire. Unfortunately, it's also so badly done that whatever satire was intended is buried in the underlying stupidity of the post.