Robertson is half way there
Robertson is right to say that Priscilla, Queen of the Desert portrays various racist, sexist and essentializing tropes of authenticity. For instance, the way that the aboriginals were portrayed as stragglers of society who dwell in the desolute parts of Australia. They are filmed as quite passive subjects as they are depicted as silent, smiling dark figures against a fire. However, I do not believe that Robertson is correct in saying that these tropes were needed in order to position a more authentic gay identity. Instead, I would argue that a scene like the before mentioned depicts one marginilzed group embracing another marginilzed group (the natives cheering on the drag show). Undoubtebly, the film could have done a better job at not using stereotypes of woman, immigrants, and natives (i.e. Bob's wife was shown as a crazy, loose drunk).