Mass-insanity is the dominant theme of 20th Century Politics. 
Richard Koenigsberg

Death camps as insane asylums (Hannah Arendt)

Only people no longer ruled by motives of self-interest could indulge in convictions that “for practical purposes (winning the war or exploitation of labor) obviously were self-defeating.” 

        "Observed from the outside victim and persecutor look as though they were both insane and the interior life of the camps “reminds the onlooker of an insane asylum.”