There is a ghost wandering countries, societies, and even the halls of academia. It is the ghost of tribalism and that ghost is as old as the dawn of the human species.
One of the defining characteristics of people around the world, is to group ourselves for our own ben- efit. Since before any civilization could be described as such, we bound together to defend ourselves from other humans, for cooperating to seek food, to build our shelters, and many more things. That is why we fought wars, conquered territories, subjugate others, and developed characteristics that define ourselves based on physical appearance, behaviors, and beliefs. That is why we developed a well-defined language to communicate, dressed in certain ways, and unified behind a particular set of religious beliefs or political systems.