You know what a sure sign somebody has been brainwashed by their church?
You can tell just by word usage. They speak with words like "thou", "thy", add "eth" to the end of words, and use the words like "holy" and "faith" a disproportionately high number of times. No person who is actually coming up with their own ideas speaks like this anymore. To me, by talking like this, they are subtley inferring that they are full of **it.