Reading accounts of the long struggles between Christianity and Islam, and the savagery each religion has wrought upon the other, it is easy to become discouraged, to see this history as the definitive clash of civilizations, which has no obvious ending except in an apocalyptic showdown. For each side, accounts of the destruction of communities add to the catalog of grievances: Muslims lament the loss of Spain, al-Andalus; Greek, Arab, and Armenian Christians recount in nostalgic detail the homelands from which their ancestors were expelled, or where their communities suffered collective martyrdom. Western conservatives parade stories of jihad and dhimmitude. None of these stories are necessarily false: throughout this history, great crimes have been committed. Yet for all this, the histories of Christianity and Islam remain quite inextricable, and repeatedly, even in dissolution, each faith has shaped the other. Underlying the struggle between Christians and Muslims is the fact that theirs is, ultimately, a conflict within a family, and no feud is more bitter.
-Philip Jenkins, The Lost History of Christianity, p.206
Girard always says that we fight with each other not because of our differences, but because of our similarities and close proximity to one another. Virtually no fight has been so passionate as the one between Muslims, Jews, and Christians. Even clashes with militant atheist communism has never been as fierce.
If you have an obnoxious coworker, it is not too much work to ignore them and go on with life. If you have an obnoxious mother-in-law, it’s much more difficult. When Muslims and Christians fight, it’s a family feud.