I know this is a sensitive topic, so please don't go overboard.
IMHO, religious people have a few extra vulnerability than people who are NOT religious
* They are willing to go on faith, i.e. believe in something without proof
* They have extra circle of relationship (i.e. besides, friends, family, acquaitances, but one between acquaintances and friends known as "fellow church-goers")
It is no surprise that Bernie Madoff went after Jewish charities and churches for his initial victims. I think even WSJ called it "affinity Ponzi" where affinity scam relies on friendship / religion commonalities to get close to clinch the scam. And more recently, Ephren Taylor, the "black Madoff", also went after black churches and such.