Leftists in the USA have built neither a mass communist party nor a mass social democratic party. The Red Purge of the fifties was so successful that few Reds remain in trade unions. There are only two institutions that leftists have managed to "capture" through a "long march" in the USA: academia and mainline Protestantism.1 The former has been a target of Horowitz for a long time, as its conquest was never complete, its summit (boards of trustees and top administration) firmly in the enemy camp. It's only a matter of time before he turns to the latter.
Cockburn also contends in the aforementioned article: "Coalitions have formed to combat Horowitz's version of Awareness with superior Progressive Awareness about what is good or not so good about Islam" (27-28 October 2007). This I doubt. Rare are secular leftists who, though quick to point out what's "not so good" about Islam, wouldn't stumble if asked to explain what's "good" about it.
Average secular leftists are, in reality, as uncomfortable about encounters with Muslims as rightists. They, unlike rightists, tolerate Islam and even defend Muslims when they become victims of right-wing Islamophobia, but that is as far as they are willing to go. They still think it is a "tragedy" that Muslims, especially Muslim women, adhere to their faith, assuming it to be inferior to their own secular ideology: "Liberal-Leftist Islamophobia Watch (Part I)," Ihsan, 18 September 2007; and "Left-Liberal Islamophobia Watch (Part II)," Ihsan, 23 October 2007.2 That won't do. We expect the religious to recognize that the irreligious are morally equal to them. So would they in turn. Unless and until secular leftists realize that Islam is as good a theology of liberation as Christianity and historical materialism, and vice versa, solidarity won't be forever.
1 Left-wing Jews might have "captured" at least Reform Judaism if not other branches had they remained within their faith community, but they have tended to reject their faith altogether. Indeed, Zionists' hegemony of major institutions, secular or religious, that claim to represent Jews is so complete that some Jewish leftists, exasperated, would even consider resigning from "the Jewish people":
Did you ever wonder what your last thought would be just before you died or believed you might die? Well, I did, and a few years ago in the waning moments before going under the knife for a life threatening operation I got my answer. As the nurses wheeled me into the operating room, what burst upon my consciousness was not, as might be expected, the fear of dying but a terrible angst at the idea of dying a Jew. I was appalled to finish my life with my umbilical cord still tied to a people with whom I can no longer identify. That this should be my "last" thought greatly surprised me at the time, and it still does.2 For secular leftists' criticisms of Islamophobia on the Left, see, for instance, Deepa Kumar, "Danish Cartoons: Racism Has No Place on the Left," MRZine, 21 February 2006; Deepa Kumar, "Fighting Islamophobia: A Response to Critics," MRZine, 3 April 2006; Richard Fidler, "Ontario's 'Sharia Law' Controversy: How Muslims Were Hung Out to Dry," MRZine 27 May 2006; Rami El-Amine, "Anti-Arab Racism, Islam, and the Left," MRZine, 3 September 2006;
What did it mean . . . and why is it so hard to resign from a people? (Bertell Ollman, "Letter of Resignation from the Jewish People," Dialectical Marxism)