Would Hollywood finance Star Wars, Guardians of the Galaxy, or Jupiter Ascending if the alien races were black or Asian? I'm guessing no.
Because that would make the aliens too "alien," presumably.
This led to the following discussion:
Although, George Lucas caught hell for making his alien races black and/or asian stereotypes, so they'd have to be very careful about it.
Same thing in the fantasy genre: Harry Potter, Lord of the Rings, How to Train Your Dragon, etc., etc. There's no reason whatsoever that elves, dwarves, or fairies should be white.
Hardcore fans say, "We love these genres as long as the most challenging thing we have to deal with is white actors in makeup."
I wish the Na'vi weren't so humanlike, but they're a step forward. If only the humans in Avatar weren't mostly white.
The point applies to humans in sci-fi too. For instance, why wouldn't the Chinese dominate space travel 300 or 3,000 years from now? Who knows, but it's certainly possible.
But aliens are supposed to be strange. The point of sci-fi aliens is to challenge us to think differently. So there's really no excuse for making them the white male norm seen in American media.
A double-edged sword
A couple of friends double-teamed me:
Oh, and a lot of the actors in Lord of the Rings were Maori.
I understand the problem of portraying minorities as aliens. You'd have to proceed carefully, but I think you could do it.
Doctor Who visits worlds that may or may not be Earth a million years in the future. There's no reason the cast of such an episode couldn't be black or Asian.
Firefly was set in a hybrid Anglo-Chinese universe. Many of the background characters and crew could've been Chinese.
Some major world in Star Wars like Coruscant or Corellia could be predominantly black or Asian. Etc.
A lot of the supporting or "guest" worlds on Star Trek could've been black or Asian. Like Betazoid in ST:TNG, Bajor in DS9, or Ocampa in Voyager. These worlds had a range of characters and wouldn't necessarily be pegged as exotic or inferior. Some characters would be good and some would be bad, creating a realistic sense of diversity.
For more on the subject, see Missing Aliens in Star Trek and Colonialism Inspired Science Fiction.