Was the nigger actually nigging when he called him a nigger? This matters very much to my opinion of the case. e.g. if you go up to a nigger smoking a cigarette on the subway and call him a nigger, you are justified in doing so However, if you just see a random black person on the street and call them a nigger for the sake of calling them a nigger, I would understand if they punched you in the face, same way I'd punch a random nigger who came up to me and called me 'crackah'