Kill them before they get you killed.
That is my trumped-up takeaway from Cass Sunstein’s post On Ethnification:
A key question here is whether the relevant social norms impose pressure to identify in ethnic terms, or not to do so. It may be “politically correct” to broadcast one’s ethnicity, or it may be politically correct to hide it. Sometimes the governing norms shift abruptly. When this is so, there can be intense pressure to self-identify in ethnic terms, sometimes to retain friends, sometimes to obtain material advantages, sometimes to save one’s life. “Identity entrepreneurs” of various kinds can increase the pressure to emphasize ethnicity. It follows that ethnic identifications may well be a product of contemporary pressure, and have little to do with anything ancient or primordial.
Alternatively, heed them at your peril.
Note that identity entrepreneurship is part of the shtick of many abominable people, especially the worst of them.