Andrew makes the observation that – Peoples stated philosophical and religious adherence may bear little relationship to their ability to work together or their common hopes for society.
This is true depending if their common hopes for society are the same as the other groups in society. But if they want to make society over to suit their favoured ism then sooner or later when they become powerful enough to do that their ability to work together with other non ism groups can descend into civil wars or acts of terrorism.

Andrew also states in this article – Perhaps our passions and aspirations, our deeply felt values are more truly us than the labels we wear.

This is really just another way of saying we are all human, the brotherhood of man kind of thing. While this also is true that as human beings our needs and the kind of life we wish for ourselves and our families is identical. The key word for conflict here is family, blood ties,tribes, we will do whatever it takes to make sure we have adequate control of the resources we and our bloodlines need to survive. As humans we also have that trait in common.