A Christian Arab (e.g. a direct descendant of Crusader Knights) What makes you think that? Christians were populous in the Middle East long before the Crusaders came - especially in Lebanon, Syria, and Iraq.
I'm sure you're right that there were remnant Christian communities, but I've been told by both Lebanese and Syrian Christians that I've known that much of the present Christian (Maronite Catholic) populations in both those countries descended from people who were re-converted during the time of the crusades. Many claim descent from crusaders who inter-married with the local Arab population.
I apologise for taking some poetic license and overstating the case for effect, but I still think the selection of an American Army Ranger of Christian Arab descent to help head up this command is going to get the attention of more than a few muslims.