Andrew Breitbart gives a great crash course in cultural/social Marxism aka Critical Theory

Leftists use political correctness/social justice and identity politics as a way to implement Marxism. Pretty much everywhere we turn today, social justice reigns supreme and activists know the best ways to execute this, is through "entertainment", "news" & the "education system".
It's not JUST about race. It's any identifier that the left deems has been oppressed. A few examples: Sexual orientation, gender, religion, disability, economic status and even whether a person is right-handed or left-handed(not kidding).