Clashes of civilizations or of religions? (#213, Topic R)

Ever since I initiated this blog, I debated whether I should set up a topic R, for Religion. My preference has been a resounding negative, but recent events suggest otherwise, to which I have unavoidably succumbed. Our retirement community has a Fireside Forum, a monthly lecture series where interesting topics/speakers are featured. Sunday, 9/10, a professor of government at a local university talked about "American Foreign Folicy: Myth and Reality," to an almost full-house (with some 500 attendeeds). He began by offering three factors: (1) threats have become deadly, (2) there are limits to international organizations such as the United Nations, and (3) USA, as a superpower, has a unique role to play. These factors, it seems to me, are code-names for interventionism, unilateralism, and exceptionalism, respectively. (Our speaker was introduced as a "Truman democrat.") After some 25 minutes, he concluded his talk and began a Q&A period. Since the speaker earned his PhD in Political Science from Harvard, I could not resist not asking a question (which turned out to be the next to last for the evening), on the assumption that the professor named in my question might be our speaker's dissertation adviser. I asked: Samuel Huntington talks about clashes of civilizations; in effect, they are clashes of religions. Given that both Christianity and Islam are monotheistic religions, how do you reconcile the two in terms of world peace? He looked at me (I was sitting at the 3rd seat on the 2nd row), and answered by citing struggles in India and said that the problems nowadays are within a religion rather than between religions. Realizing that this answere might not be satisfactory (since India's religions are not monotheistic and my question was on Christianity and Islam), he quickly added: "I disagree with Huntingthon." Why so or in what aspects he disagrees with Huntington, our speaker did not say. He then moved to the last question and called an evening.
During his talk, our speaker touched upon the Pew Foundation. It so happens that, just a day or two before, I read, on-line, an interview of Huntington by the Pew Foundation on Reglion. The interviewer's questions were rather sharp, putting Huntington in a corner. At the end, he had to admit: "Christianity is a missionary religion." As to my question to the speaker for the evening, which is relevant to a long-term research project I am doing, I have to wait for another occasion.