Hannah Arendt and her famous dictum

Hannah ARendt famously said:  “If one is attacked as a Jew, one must defend oneself as a Jew.”   I have been thinking about that as of late.  So if someone is attacked as a Shi`ite or Sunni, the person is obligated to defend himself/herself as a Shi`ite or Sunni, for example?  But why? Why is it an obligation? Why can't one defend oneself as a human being, for example? That requires an article.