On overlooking the wrongs of those "on our side" (Orwell)

I have little direct evidence about the atrocities in the Spanish civil war. I know that some were committed by the Republicans, and far more (they are still continuing) by the Fascists. But what impressed me then, and has impressed me ever since, is that atrocities are believed in or disbelieved in solely on grounds of political predilection. Everyone believes in the atrocities of the enemy and disbelieves in those of his own side, without ever bothering to examine the evidence. Recently I drew up a table of atrocities during the period between 1918 and the present; there was never a year when atrocities were not occurring somewhere or other, and there was hardly a single case when the Left and the Right believed in the same stories simultaneously. And stranger yet, at any moment the situation can suddenly reverse itself and yesterday’s proved-to-the-hilt atrocity story can become a ridiculous lie, merely because the political landscape has changed.—George Orwell, A Collection of Essays, 191