I'm not sure what you intended with this phrasing, but it's a very wrong and provocative one (though you likely did not indent that). The Holocaust's victims were by and large not citizens of Nazi Germany. Jewish residents of Germany were stripped of citizenship in (as I understand) 1935—mirroring President Trump's promise to systematically strip citizenship of American-born, non-white immigrant descendants. Nazi-era Germans did not view German-born Jews as "citizens" by any possible torturing of that word. White nationalists, in the United States, do not view many non-whites as citizens of America, even if they were born American and lived their entire lives in America, as American citizens.

The distinction between "true citizens" / "external foreigners" is not a footnote to the Holocaust; it's the central thesis of German Nazism, that subgroups of people native to the German region were foreign aliens without true loyalty or allegiance.

(This more of a tangent, but the majority of the Holocaust's victims were not even German residents; they were captured and murdered from other European countries Nazi Germany invaded and ravaged. Auschwitz' victims, for instance, were almost entirely from Central and East Europe. The wording you chose, elevating the "citizen" above the "foreigner", as if concentration camps for foreigners is some second-class, not-100%-full-on-Nazi thing, is a disturbing language for one familiar with the German version).