Her new book, Fields of Blood: Religion and the History of Violence, she aims to evaluate the historical truth of this declaration.
For this project, she first surveys truly ancient belief systems -- Central Asian Zoroastrianism, Aryan tenets developed on the Indian subcontinent, and the Chinese Daoist and Confucian principles -- before going on to look more deeply into the place of violence in societies of the Abrahamic religions of the Book: Judaism, Christianity, and Islam.
Of course, none of these started out as what we think of as "religions." All these systems which shaped and gave order and meaning to human life, society, and the cosmos were total and experiential and certainly not creedal.
Moreover, all these pre-modern "religions" grew up in agrarian societies subject to inherent conflicts that embedded contradictions within them. According to the anthropology Armstrong adopts, when humans lived as pastoral nomads, life was pretty much hand to mouth and roving bands had little hierarchy. (She does not discuss whether this equity should be imagined for women as well as productive male hunters and herders.) But with the development of settled agriculture came social differentiation.
That is, "religions" came to embody both admonitions to community, order, and justice alongside coercion, force and damnation. It is through this lens that Armstrong surveys such murderous episodes as the Hebrew celebration of the conquest of Canaan (probably mythical), Constantine's institutionalization of Christianity in the Roman empire, the Crusades and the Muslim conquests of much of the world in the 7th and 8th century.
Probably the least familiar parts of this material to people in this country is her explication of developing contradictions within Islam. Here's a representative nugget describing early intra-Muslim wrestling over the relationship between Mohammed's revelation and the order-enforcing authorities:
Armstrong concludes that contemporary Westerners see religion as a source of violence because so much of the world is engaged in responding to the industrial-age secularization of politics that we came to gradually in the 18th century. For the developing world, especially but not only its Muslim peoples, keeping a death grip on the more bellicose tendencies implicit in their traditions is a defensive posture assumed to counter imperial aggression. That is, in this, the Taliban are responding to the same stimuli as Bible-thumping fundamentalists who deny evolution and seek to enforce patriarchy: both are recent creations of modernity fighting engulfing, unwelcome change.