Julian Sanchez adds to this post by Thoreau:
It’s [Muslim] urbanites and cosmopolitans who are most likely to come into contact with the many variations between the local versions of Islam. Now, if you’re a believer convinced that there’s one uniquely authoritative set of commands and practices that have been divinely ordained, this can provoke enormous cognitive dissonanceand prompt a search for the “true” version of Islam purged of all these regional variations. Insofar as this also purges the system of its evolved adaptations, the result is apt to be more radical, and potentially more dangerous.