The war in Russia was overall far less civilized than the war in the west. There were a lot of scores to settle at the end.

Rape was perhaps an additional way of debasing the german population at the time. On the eastern front life was worth very little. The political system of the times in germany tried to justify general atrocities by calling the russians basically animals. I think with what transpired in those years may have induced russians to act the part.

For any combination to have attacked the russians would have been wrong. The russians bore the brunt of breaking the german army. Without the russian involvement and sacrifices there was not much probability of the western forces defeating the german armed forces.

Even if they had managed it the causualties would have been too high to accept. I forget the total amount of russians that perished but it was really a signifigant percentage of their population. Expecting the russian army to let bygones be bygones was basically impossible.

Even with the low losses experienced on the western front. General Eisenhower is credited with starving approximatly one million german soldiers to death. This was after germanys defeat. War is far from sugically clean. It in fact is a very dirty business.