I like that you're quoting one of Ayn Rand's "Communist" talking points rather than talking about Communism proper.
Let's get something straight. There is no Communist-central plan. Russia and China each approached Communism differently. If somebody else were to try Communism, they'd have a completely different approach to it. As it is, the only Communist regimes we talk about are the ones installed by violence, and as a result we get this idea that you can't have Communism without violently murdering people. The smaller communes that manage to last decades without violence, they're the ones we ignore when readying our anti-Red talking points.
You're showing a fair spot of anti-intellectualism when you bash abstract philosophy. Who do you think invented capitalism? I'll give you a major hint: He was an abstract philosopher. Adam Smith was just like Karl Marx, only we like him more. Every major idea we've seen in the world stems to some degree from abstract philosophy, as you call it. It's not particularly abstract, mind you, because it has concrete effects on the world. We're not talking Nietzsche, here.
Now, let me explain why the Holocaust is really so touted, and why Mao isn't mentioned as much. Partly it's because Germany is a European nation, and the world is still very Euro-centric. In bigger part, however, it's because the Nazis did a pretty good job at its attempt to exterminate the Jewish religion, which, though small, is a pretty major force in the world. People still think Judaism is one of the three major religions in the world, because they like ignoring Hinduism. Jewish people are usually well-educated, hard-working, and ambitious, which is why there's still a disproportionate amount of them in executive positions at companies, in top-notch colleges, and in the literary world. (If we go by the utterly lame judge that is IQ, the average IQ of a Jewish person in the United States is higher than of any other arbitrary demographic, including asian.)
There were 18 million Jews when Hitler took power. When his regime was ended, one in three of those Jews were dead. Remember Nazis also killed 5 million Protestants, but nobody cares about that, because there are so many Protestants. Hitler showed a lot of Jewish people the mortality of their faith. In a time when Jews were still hated in most parts of the world—and they were certainly still hated in the 40s—they were dealt an enormous blow.
So a lot of well-educated and influential people all took up the cause. We've got literary masterpieces regarding the Holocaust. I can't think of any that have to do with other genocides; if they exist, I haven't heard of them. There's Eli Wiesel's Night, there's the diary of Anne Frank. Authors wrote a slew of kid's books about the subject, so that a lot of us grow up with the Holocaust ingrained in us. Number the Stars; the Devil's Arithmetic. Those are the books used to teach 10-year-olds about morality. It's all Holocaust-based, because many of the best kid's book writers are Jewish. (Even the ones that don't make being Jewish a big part of their writing. My favorite Child's Lit author is Daniel Handler alias Lemony Snicket, one of whose adult books is about the Golem in the Jewish religion.)
Finally, we have the fact that World War II is perhaps the best and easiest story ever told. We've got a brilliant military leader and outright psychopath whose childhood is tragic and fascinating, whose seconds-in-command were all rich characters, and whose uniforms were all made by Hugo Boss, still a big name in the fashion industry. There's the famous swastika. Then there are Hitler's allies: Mussolini, who's almost comically corrupt and bad, and Hirohito, the faceless emperor of a nation that was batshit insane when it started fighting and that tortured American soldiers in unspeakable ways. On the other side you have the heroic crippled FDR, and the brilliant procrastinator Churchill, and you've got the morally uneasy compromise with Stalin. It's a made-to-go movie, which is why so many movies are made about it. Whereas World War I was hell, World War II had a very clear villain. And how do we know he's a clear villain? Because he's cooking Jewish people in ovens.
So World War II is an easy story, and it all revolves around the Holocaust as proof of our moral superiority. Therefore, the Holocaust gets celebrity attention, which complements nicely all the talented Jewish people who remember the Holocaust because their parents died in it.
(I'm saying all this as a kind-of Jew who grew up listening to a different Holocaust survivor each year. Apologies if that colors this narrative.)