I really don't think that was the case for Juliet. She's a doctor; she took the Hippocratic oath, and that meant something to her. She goes and tears a strip off Jack for not helping, and that had nothing to do with Sawyer. And Sawyer was the one who says he's doing it for Juliet--Kate comes and offers to take him to the Others, and then Juliet sends Sawyer after her to help.