One of the academic advisers on my dissertation committee was vigilant against personal bias. He went (probably still does) so far as to recommend studying a place you hated. In geography, most scholars do research in a location they love, which might cause you to push your work towards expected results. A tool that can help a scholar guard against seeing what you want to see is the null hypothesis:
Retaining talent is an effective approach to regional workforce development.
Instead of debunking brain drain myths, I look for an underlying rationale for the concern and functioning brain drain plugs. For example, brain drain is costly: