Really? I guess you haven't heard of the American POW's massacred near Malmedy during the battle of the Bulge where 72 American Soldiers were lined up in a field and machine gunned by a German SS unit and then buried in some deep snow. That's at least one example.
There are always at least some atrocities in any war. But there's a big difference between atrocities committed in the heat of battle, or by soldiers acting on their own initiative, and atrocities on a large scale deliberately planned and ordered from the top. Large scale murders in violation of the Geneva Conventions were Soviet policy, coming down from Stalin himself.
A BIG difference.
With all due respect, comparing the 72 murdered POW's at Malmedy with the systematic murder of hundreds of thousands of POWs by the Communists is like comparing apples and aardvarks.