Lebanese people who are Druze, Maronite Christian, Greek Orthodox, Catholic or Baha'i still look "Arab". You can't tell what religion a person is by their appearance, unless they have earlocks, or they're wearing a burka or religious robes. There are also Iranians who aren't Muslim, although admittedly there aren't that many of them, particularly since 1979.
However, even if they were Muslim, that's not surprising as there are plenty of religious hypocrites of all stripes. I've known Christians who have committed heinous crimes, and I've got some Jewish friends who eat pork.