Well, I noticed that several other bloggers are using xenophobia today; however, there are only so many "x-words" and I had decided that this last night, so here we go!
As a historian, xenophobia has a special significance for me, although the phrase used in the literature is usually "the fear of the Other." All cultures exhibit this fear; "Humans destroy what they fear" is an old saying and frequently reused in literature and cinema such as X-Men. This is not merely confined to European cultures, either. For example, the name that each american Indian tribe used for itself translate as "the People." Other tribes were not really "People." This allowed for fighting between neighbors.
Part of the fear is instinctive; humans are actually fairly conservative creatures fearing change. Also, our minds work in loops that start with observation and move to contemplation. A decision is made and implemented. Confronted with something that was experienced previously (or at least similar to something known), this operation is practically instinctive. Faced with something odd or unique or radically different, fear and indecision set in as we try to cope with new input. The easiest solution is to destroy.
This explains propaganda in warfare. The enemy must appear "unhuman" to effectively convince the populace to kill. It taps into that fear of the other; confront with something different, it is easier, best, safest to kill it.
"What does this have to do with gaming?" you ask. Good question, and I don't really have an answer. I've wracked my brain looking for a connection, maybe something about how parties seem to slaughter orc children all the time or argue about whether it's a LG chore or not. But if one's brain is hardwired to work in this way (and remember that our instincts frequently short circuit and bypass our reason), is it even a moral issue?
AC: -2  Special: Surprise, immune to fire/cold
HD: 7+7 Move: 9
Attacks: Claws (3), bite HDE/XP: 9/1100
Xorns are a race that is native to the Elemental Plane of Earth, but they occasionally travel to the deep places of the Prime Material Plane to search for the precious metals that they enjoy as snacks. A xorn is able to adjust its molecules and pass through solid stone as if it were air; it can also do this to attack by surprise (5-in-6) from underneath or out of a solid wall. Its claws do 1d6 damage, but its powerful bite does 4d6 damage! A xorn is also completely immune to fire- or cold-based attacks and takes no more than half damage from electrical attacks (if it saves against an electrical attack, the damage is 0).
A xorn does have special weakness to some spells. Move earth stuns the xorn for 1 round, in addition to knocking it back 30 feet. Transform stone-flesh or transform rock-mud drops the xorn's AC to 8 for 1 round round and effectively stuns it (losing its next attack) since the xorn must readjust its molecules. A passwall spell causes 11-20 damage.
Fortunately for most adventurers, xorn are relatively peaceful. They will merely demand a "tribute" of precious metals (copper, silver, gold, etc.) from any groups they encounter and will then allow the party to pass on without incident. Note that they can smell precious metals from 20 feet away, so the party can't lie about what metals they have.