How Does the Presence of Particular Ethnic or Religious Communities

How does the presence of particular ethnic or religious communities with legacies of persecution or repression aid terrorists?

A) People in such areas are likely to turn terrorists in.
B) Such groups are unlikely to give the terrorists new recruits but they may give them resources.
C) These communities would not give terrorists tribal support (they are, after all, terrorists) , but they appreciate the religious guidance terrorists provide.
D) They may also create "black holes," where terrorists can hide.