On religious extremism

Religious extremism: the good, the bad, and the deadly by Lawrence R Iannaccone
  and Eli Berman from 2005-2006

 Abstract: This paper challenges conventional views of violent religious extremism, particularly those that emphasize militant theology. We offer an alternative analysis that helps explain the persistent demand for religion, the different types of religious that naturally arise, and the special attributes of the “sectarian” type. Sects are adept at producing club goods – both spiritual and material. Where governments and economies function poorly, sects often become major suppliers of social services, political action, and coercive force. Their success as providers is much more due to the advantages of their organizational structure than it is to their theology. Religious militancy is most effectively controlled through a combination of policies that raise the direct costs of violence, foster religious competition, improve social services, and encourage private enterprise.

 A recent discussion about British politics which partly uses the above paper
Irrational politics: is it about signalling?

Check also Eli Berman