You did a lot of hard work, researching second-hand. Allow me to offer two insights.  

In Doctor Zhivago (the movie), the doctor has been kidnapped by irregulars fighting for the Reds.   He rides with them for about a year during the civil war. They are about to set him free when a commissar from Moscow comes along. The commissar and the guerrilla commander argue. The commissar reminds the commander that when the civil war is won, he (the commander) will be judged not on his heroism but on his political correctness.   That antedates Stalin.

Here is an example of political thinking, incorrect and correct. A self-identified feminist says that the time has come to end the oppression of women by men and guarantee equal pay for equal work.  The politically correct Marxist points out that whether a society is patriarchal or matriarchal is a historical fact based on the objective conditions of their economies.  In our society, men and women are both oppressed by capitalist exploitation, only that their gender roles exploit them somewhat differently; and, moreover, the "conflict" between "patriarchy" and "feminism" is a ruse created by the ruling class to divide workers against each other so that they do not identify their true common enemy.  

The reason that you do not like country-western music is that you never drove a truck, you've never been divorced, and you never were in jail.

Steve, your inability to understand what I write is amusing. I pointed to the movie Dr. Zhivago as a reference to Marxism circa 1920.  "Political correctness" was not invented by Stalin.  Now you claim that it was invented by Mao Zedong, but the speech cited may have come from 1939 or 1959. And in any case, he was speaking in Chinese, which was translated into English for our convenience.  So, we have no idea what he "really" said. I still maintain that political correctness as a concept in Marxism did not come from Joseph Stalin, who was never a theoretician. 

The point is that political correctness does identify an important concept.  The concept was invented by Marxists. We agree on that much.  You seem not to understand it. Much of Ayn Rand's criticisms can be understood based on it.  The conservatives - whatever their patriotism and support for a free market - are not politically correct.  I have pointed before to this essay, "Defending Capitalism against Ayn Rand"  which provides several examples of how Rand was influenced by the ideas of the Russian Revolution.

Read Pasternak's biography in Wikipedia.  He was an older contemporary of Ayn Rand.  He wrote Dr. Zhivago at the end of his life.  Note, also, that it was never intended as "anti-communist." In fact, it was well received by communists in the West.  

How much Lenin have you actually read?  Have you even read any of Das Kapital?  You seem to be getting your knowledge second hand. What would you say to someone who analyzed the ideas of Ayn Rand based on the books about her, but never read actually read any of her works?

Steve, as I said, you did a nice bit of work, a lot of research.  Most of it was second hand.  That is why I quipped at the end about your not liking country western music because of your never having been divorced, driven a truck, or been in jail.  You again missed the point:  You never read (much) Marxism first hand. Over a Thanksgiving in 2007, I read Vol. 1 of Capital.  It was a bit late, but I got around to it.  I had  long since read Imperialism and Leftwing Communism: an Infantile Disorder by Lenin, as well as the essays by many of those leftwing anarchists. For years, I had three editions of Mao Zedong's Red Book, in English, German, and Chinese. I could go on...  The point is that I did my reading first hand. You did not.  

You endorse the work of David Horowitz with no standard for comparison, calling him "perhaps the leading expert in communism in this country for many decades." How would you know?  Compared to whom, and by what standard?

He certainly did well at promoting himself.  Reformed and repentent Marxists are easy to find. My favorite was Christopher Hitchens, but only because I do not know as much from the authors of The God that Failed.  Then there are all the neo-conservatives, liberals who during the Reagan Revolution came out for an aggressive U.S. foreign policy.  (Hitchens also advocated for the wars against Iraq.)  

My failing here is that I never heard of David Horowitz until you mentioned him.  I read his biography in Wikipedia.  As I said, he promotes himself well. And, as the cliche reminds us, no one is more dogmatic than a convert. 

The concept of "political correctness" seems to have been invented by the Bolsheviks. Who was first has not been established. You claim - via Horowitz:

Upon Stalin's death, Mao Zedong came to think of himself as the natural leader of what should be the "correct" Marxist thought.

David Horowitz points out that "Political Correctness" was actually a phrase coined by Mao Zedong and referred to official line of the Chinese Communist Party - "the Party Line."

As I said, you did some nice work.  You were just wrong about a detail.