The Predator should be the mysterious outlier, as contradictory in character as his technology and primitive culture is.
One of the best parts of Briggs script is that he emphasizes their contradictory nature. "They look like bushmen decked out in sophisticated hunting equipment." And the like.
The whole Arcturian's are aliens thing is actually rather sickening when you understand Camereon's intent with the line. Like was stated previously he was drawing Vietnam Parallels there.
IE, this was basically like that one scene in Full Metal Jacket where Joker tells his buddy Rafterman "Half these gook whores are servicing the Vietcong, the other half have TB. So make sure you only f**k the ones that cough."
IE: The Arcturian colony is full of sub-human trash, and it doesn't matter if they're transexuals, dudes, or chicks. Maybe it's like space Chicago or something...