User blog comment:Thailog/Ep. 202 "Earthlings" discussion/@comment-1770843-20120506104608/@comment-1839689-20120506234434

I think it's interesting that Superboy seems to be think of "Earthling" as being the same thing as "human". It makes sense on some level as humans do make up the vast majority of Earth's intelligent population. Since he has reasons to dislike just where his human heritage comes from, he didn't like being referred to as an Earthling. Sardath, however, is looking at the term the same way you are, like a nationality. It may just reflect how mindsets on the matter change after interplanetary travel, and therefore immigration, become more common.