Tell the difference between understandable “cultural differences" vs inconsiderate, mannerless ignorance?

My coworkers/housemates R about 90% from1 particular impoverished country (for this venue, I'll call it "Venus"). Of that 90% about 80 % of those R Muslim. 2 of many possible examples: They pray in Islamic chants, often not in the bedroom/other private area. In a congested area of the living room they say that praying facing east is necessary. Is this the only area in our house that faces east? I have been told to turn the TV which is at a normal level--down or mute it b/c it's interfering with their “focus on Allah”. Another: There’s a store down the street from the building I work in. Every time I go to the store, I ask if anyone needs anything b/c it’s quite a hike. Whenever when they go, they only ask others from Venus what they may need. I've asked them why & they say it's "cultural". Americans say "It's cultural yes but, only b/c you're female and not to be respected by their culture." How can I tell if a behavior is cultural or the person's just an azz? What do you think?