It always comes down to this. What makes those damn Jews think they are so special that "their" genocide gets all the ink.
What Makes the Holocaust Unique...
"The "Final Solution" was designed to exterminate every single Jewish man, woman and child. The only Jews who would have conceivably survived had Hitler been victorious were those who somehow escaped discovery by the Nazis.
Jewish birth (actually mere evidence of "Jewish blood") was sufficient to warrant the punishment of death. Fackenheim notes that this feature distinguished Jews from Poles and Russians who were killed because there were too many of them, and from "Aryans" who were not singled out unless they chose to single themselves out. With the possible exception of Gypsies, he adds, Jews were the only people killed for the "crime" of existing.
The extermination of the Jews had no political or economic justification. It was not a means to any end; it was an end in itself. The killing of Jews was not considered just a part of the war effort, but equal to it; thus, resources that could have been used in the war were diverted instead to the program of extermination.
The people who carried out the "Final Solution" were primarily average citizens. Fackenheim calls them "ordinary job holders with an extraordinary job." They were not perverts or sadists. "The tone-setters," he says, "were ordinary idealists, except that their ideals were torture and murder." Someone else once wrote that Germany was the model of civilized society. What was perverse, then, was that the Germans could work all day in the concentration camps and then go home and read Schiller and Goethe while listening to Beethoven."
You're right, that's a major factor. Though I generally think prosecuting things like this is a mistake, there's another major difference as well. To a large extend, the nations in which communist atrocities occured, and their populace, are disinterested. For example, the reason that communists who committed atrocities in the Soviet Union aren't prosecuted, and that their crimes are forgotten lies in those nations, not in the US and not in the Jewish community.
And you think that it justifies censorship? The Soviet system was on the other hand designed to exterminate an entire class of people. Is it therefore better? Is a system which murdered well over 100 million people, destroyed lives of billions and poisoned minds all over the world better because it had different goals?