The rightists of the opposition bloc are not Nazis but Russian (etc.) rightists who were within the Soviet Union or fled from it. I don't endorse the "Nazi collaborator" claim, though I think the characterization of "show trials" is also ridiculous, as demonstrated by the much worse nature of the secret trials carried about by the Khrushchevites. Frankly, when I am feeling masochistic, I prefer reading about the opposition bloc stuff than the foreign fascist collaborator accusations.

Also, like, reading the comments of the very thread you link is a good idea.