What word describes the dislike of non-human (extraterrestrial) species?

Solution 1:

I think xenophobic is the best choice. Take this definition:

xenophobic - having abnormal fear or hatred of the strange or foreign

Extra-terrestrials are definitely foreign and most likely strange too.

Solution 2:

If you're looking for a word that doesn't necessarily imply a strong hatred or fear of another group (like xenophobic), but instead an elevation of one's own group to a higher level of importance, then I would lean towards anthropocentric (mentioned in a comment by FumbleFingers) as a better alternative:

Anthropocentric:

1. considering human beings as the most significant entity of the universe
2. interpreting or regarding the world in terms of human values and experiences

Another possibility may be humanocentric:

In science-fiction, humanocentrism is the idea that humans, as both beings and a species, are the superior sentients. Essentially the equivalent of race supremacy on a galactic scale, it entails intolerant discrimination against sentient non-humans, much like race supremacists discriminate against those not of their race. This idea is countered by anti-humanism. At times, this ideal also includes fear of and superiority over strong AIs and cyborgs, downplaying the ideas of integration, cybernetic revolts, machine rule and Tilden's Laws of Robotics.

Solution 3:

It seems clearest simply to say that someone is anti-alien. Not only does that spare them from having to stem xenophobic, it removes the “unreasonable fear” element of a phobia and makes clear that they are taking a position against the aliens.

Solution 4:

Since it's science fiction anyway, let's coin a word:

anterraphobic

(an- not + terra, of Earth + phobic)