Since we recently discussed the phenomenon of Muslim Brotherhood and Salafi preachers warning their followers against wishing Coptic Christians a happy Easter, some reading I did yesterday may shed some light on the matter. It's from a book of essays called Global Salafism edited by Roel Meijer that contains contributions by many leading experts on the subject — Stephane Lacroix and Bernard Heykal on the Saudi variant to name but a few. The introduction refers to four "tensions" of Salafism as currently understood (that is, in its heavily Wahabbi-influenced dominant contemporary). These tensions, the author argues, have transformed a revivalist / puritan movement into one that is more politically problematic and often intolerant. Here's some screen grabs from the Kindle edition, since Amazon's Cloud Reader does not allow for even limited cut-and-paste:
There are also some interesting passages on the more recent doctrinal / ideological sources of anti-Shia sectarianism (which of course date back all the way back to the fitna but have more recent sources of revival: