I think there's truth to that; however, I wonder if there can also sometimes be a sort of "immune system" that protects people in a sub-culture from the bad parts of the group.

For example, when I move, I ask people at my old church if they recommend any churches in the new city. So I naturally end up insulated from any crazy churches that are there. On the other hand, someone who isn't already plugged into the "Christian network" is much more likely to be exposed to the crazy parts of the community.