One of the most basic human traits is the ability to distinguish between us and them. Humans seem to have an insatiable, driving need to form tight groups that exclude others. In a way it is kind of quaint and interesting, rather like the way phospholipids tend to spontaneously form membranes. But it doesn't scale well, and the implications of this basic behavior on our culture as a whole are profoundly troubling. In almost any situation it is possible to be classified an outsider by not behaving according to expectation, and even basic safety can be beyond the reach of an outsider.