David Myers on Animosity Between Similar Groups

On Sunday, Politico published an enlightening article by Hope College psychology professor David Myers on the divide between Shia and Sunni Muslims. In the article Myers provides four points to help explain why people who share so many things in common are such enemies.
Myers also briefly illustrated his point with the historic Northern Ireland conflict between Protestants and Catholics. It occurred to me that on a lesser level, we see these conflicts arise all of time within Christianity. Charismatics and non-charismatics, Calvinists and Arminians, and so on share many points of agreement but war over the fewer differences. Myers article is well worth reading; his four basic points are:
1) No matter our similarities with others, our attention focuses on differences.
2) We naturally divide our worlds into “us” and “them,” ingroup and outgroup.
3) Discussion among those of like mind often produces “group polarization.”
4) Group solidarity soars when facing a common enemy.
Number three is a point which concerns me most about noticing differences. Such polarization can become especially hot if people fail to talk to those in the other camp. I see no problem with freedom of expression as long as we make sure everybody has it. We need to talk to each other rather than cloister and polarize further.  Myers expresses it this way:

Turning today’s closed fists into tomorrow’s open arms requires recognizing the relative modesty of our differences, finding our deeper commonalities, defining a larger “us,” communicating across group lines and discovering transcendent goals.