The generalizations are reminders of the miserable folly of every ideology, whether or not it seems congenial and corresponds to our prejudices. In real life, seeing leads to believing; in the warped fantasy world of ideology, it’s the other way around: believing is seeing. If you’re ideologically afflicted, you know what you’ll see before you look. In the words of Rick Salutin in this paper: “What ideology lacks is humility.”
I find the leftist notion that they do not subscribe to an "ideology" to be an endless source of amusement--and quite lacking in humility. And while it's true that not all terrorists are jihadis, most are, and we ignore/discount their singular ideology at our peril. As for the claim in bolds: here's hoping that, pace ideologues on both ends of the spectrum, the ideology of "life, liberty and the pursuit of freedom" has yet to run its course; our survival depends on it.
Because virtually every ideology is prone to excesses that in the end invalidate it, we’ve good reason to take to heart the assessment of John D. Cohen of the U.S. Department of Homeland Security when he warned: “What happened in Norway is a dramatic reminder that in trying to prevent attacks, we cannot focus on a single ideology.”
Those are the lessons I draw from Marmur's lesson in moral relativism. Class dismissed.