re: Hitler's "non-aggression" pacts
I can't speak for other posters, but in all the posts where the attitudes of the Left before WWII were being discussed, I, at least, was always referring to the American radical Left of that time. No other nation. They had the luxury of comment without worrying about consequences, unlike their brethren in Europe.
It's worth noting that labor unions didn't fare too well under communism either. A strike in the Soviet Union would have been severely dealt with. Jews, gays, and certain minorities were also persecuted in Stalin's Russia.
Stalin and Hitler. Tweedledum and Tweedledee as far as I'm concerned, and they battled for pretty much the same reasons.