Adopting austerity is one of the know signs of creeping radicalization and has been well-studied:
QUOTE: "Though the methodology of missionary organizations may be peaceful, the acceptance of their message increases the likelihood that youth will also accept the message of religious-political or militant groups as being absolute. For example, missionary organizations such as the male-focused Tableeghi Jamaat and the female-oriented Al-Huda, which have the largest public reach, have the potential to increase youth receptiveness to more radical groups by reinforcing messages of a primarily Islamic identity, through the rejection of indigenous ethnic, national or tribal identities as well as foreign cultural and political signifiers. By popularizing an exclusive Islamic or sectarian identity, they may contribute to alignment with more radical organizations, and the rejection of pluralistic politics." /QUOTE.
Shunning movies and music is a practical way to demonstrate the shunning of foreign cultural influences. When society rewards such behavior by accepting it as a qualification of piety rather than close-mindedness, the stage is set.