Oh, I have a good idea how some folks think. They like to identify fellow members of their community using religion. This is why, when you go up to the mountains of North Carolina, you'll stop in at many places of business and find stacks of directories, all listing local businesses that are run by Christians. People just assume that if a roofer or plasterer has a little fish in their ad, they are more trustworthy than some guy with a foreign-sounding name who's been in business for twenty years.
But what gets me is how people can be so blind to the obvious problems with this sort of prejudice. If you say "He's a Christian," I expect most Christians will create in their minds some sort of image of the ideal Christian. You know... follower of Christ, sort of like one of the Twelve Disciples or something. But let's be realistic here. Think back to all the people in history (or even the last century) who have called themselves "Christian." We're talking a pretty wide range here, folks. Everything from C.S. Lewis and Dietrich Bonhoeffer to Charles Manson and Jim Jones. Desmond Tutu to Pat Robertson. Oy vey.
It gets worse when you give a person who has "deep religious convictions" a positive response. Then you can range from Gandhi to Bin Laden.
The main thing to remember here is that in the real world, you can't assume that "religion" will automatically make any particular stranger more trustworthy than any other. You can't assume that she or he will be "on the same page" as you are, ethically speaking. I guess it all comes down to one of my pet peeves: prejudice. Once we recognize the value of our assumptions of what religion or lack of it will mean about a person before getting to know her or him, then we can put them into proper perspective. I think that will remove one serious obstacle to true civilization.