The question is not if the Nazis were the bad guys, but if the Russians were bad. I think the answer is pretty simple. If anyone has any doubts they should ask millions of starved Ukrainians, thousands of killed Polish officers, hundreds of thousands of killed eastern Europeans and millions of people sent to gulags. Oh wait, you can't...wonder why? Probably because Soviets were really such a nice group of people.
So did the Nazis, in higher quantities too: https://en.wikipedia.org/wiki/Intelligenzaktion
See also: https://en.wikipedia.org/wiki/Generalplan_Ost