I can't recall cannibalism of civilian children by soldiers on either side anywhere in the history of Poland in WWII. Can you offer a citation?
Me neither. The Russians were brutal towards captured German troops and sent German POW's to labor camps in Russia where many died. (In the film "The Pianist", the German officer who helped Adrian Brody's character was sent to Russia and died in a Soviet camp in 1952.)
And the Russians raped German women as they moved toward Berlin. They shot the Polish officer corps in the Katyn forest. But those are the only atrocities I've read about.
Besides, as I often say, the difference between western civilization and others is not the depths to which we've sometimes fallen (terrible things have undeniably happened in the west), but rather the heights to which we've climbed. We've had our share of brutality, but we've also created most of the greatness of the modern world. One can show viciousnes in the West comparable to what is going on in the Congo (almost). But there is no African Venice....no African Plato....no African Newton.