They were not "evil", that does not mean anything. The Soviet Union was an imperialist power, yes, and did atrocities indeed, but they were nothing like the nazis. We can say that the US did countless horrors too, like mass internment of japanese civilians, the nuking of Hiroshima and Nagasaki, the recruitment of nazi scientists and the general amnesty for leaders of the 731 unit in exchange for their results, mass rapes in occupied europe and so on. But they were not "evil". If you want to use "evil" when talking about reality, at least keep it for the country that led mass genocide and eugenic policies and caused the slaughter of entire populations and millions of people.

The non-agression pact was to prepare war with Germany, a war that was sure to come. And the way anti-soviet propaganda (because here it's propaganda, the number of casualties is greater than the number of people that were present this day...) is revived to show how "Russia" was always evil and how war is justified and how yeah we should hate them is a problem.