No, they were far from pure as the driven snow, far from it..
This is from August Prophet:
“..n February 1970, McCain took part in what is now known as the “church riot” after their captors denied him and his fellow POWs permission to hold a church service. His actions later led to his informal appointment as prisoner chaplain. One “lesson,” a term he preferred over sermon, concerned the prisoners’ fate, McCain recalls: “We were doing Caesar’s work when we got into prison, so we should ask for God’s help to do the right thing....”
http://www.newser.com/story/34992/mccain-recalls-pow-prayers-tests-of-faith.html
Interesting, a insight into the man:
The prisoners had developed a tap code system for communicating through the walls. Through that tapping, “we decided we needed to be all on the same sheet of music at least one time during the week,” Swindle said.
The prisoners decided that every Sunday, after they had eaten their rice, the highest-ranking officer would cough loudly and say the letter ‘c’ for church. The prisoners would then say the Pledge of Allegiance, the Lord’s Prayer and the 23rd Psalm. The psalm was said in plural: “Yea, though we walk through the valley of the shadow of death we will fear no evil.”
Prisoners used diarrhea pills mixed with cigarette ash—or charcoal or dirt—to write lines of Scripture and surreptitiously share them
http://blog.beliefnet.com/crunchycon/2008/08/the-pow-church-riot.html