When I was a new Atheist, I made the grave error of entering into a dating relationship with a 44-year-old Catholic. As I was trying to get to know him, I'd ask him questions about his beliefs and in doing that, he'd become hyper defensive and start raising his voice/yelling. So, I'd back off for a few days or a week and try to ask him about his beliefs in a different way only to have him yell at me again. Probably most people who are reading this are thinking, "The fact that he yelled at you should have made you leave on the spot" and whomever is thinking that is RIGHT! LOL
He was what I call a HypoCristian also known as a Cherry Picker or Cafeteria Catholic. I saw the blatant hypocrisy of the so-called Catholic Church (I now call it what it is--a cult) when I was a teenager and deciding at the age of about 14 that I didn't want to be part of a group of people who were such blatant hypocrites, I knew I was not Catholic.
This guy was my age and raised in the same county in NJ as I was--exposed to the same people, schools, type of family, etc. Why didn't he see what I saw? Why didn't he delve into the information as I did? Why did he refuse to watch Religulous, Zeitgiest, or go to the site GodIsImaginary.com as I asked him to? Why didn't he question me about my beliefs? Why was he so resistant to being questioned about his? Why did he get angry and tell me he wanted me to "accept him" as he was and not make him "feel defensive for being a believer"? I was just trying to understand him, to get to know him.
One day, I stopped completely because he said something to me I will never forget and that stopped me dead in my tracks. He said:
"If I say now, at the age of 44 that I don't belief any of it, then I will have been a fool to have lived my life like this ." He may as well have said, "Because I'm a prideful, egotistical asshole who would have zero morals or ethics without my religion".
The information is out there for religious to see. There are many reasons they don't look into it. There is a reason(s) you took so long to get to it. There is every reason for them to have already "for a second" question "their silly belief in this hocus pocus" yet they have not.
Why is it so important to you to make this "second" happen? I think it would be much easier for Atheists to uncover this reason and eliminate it than it would be for them to get Christians to question their beliefs. I know there are lots of Atheists who feel otherwise and consider it a great thing to talk to their Christian friends and continually debate them and I'd neither applaud or discourage that because it's up to everyone what to do with his/her time and if that's what you're into, enjoy! Personally, for me it's a waste of time. The information is out there for anyone who is interested in looking into it.
Maybe just letting them know that if they have any questions about becoming an Atheist, they can come to us and telling them that if we are reconsidering becoming a Christian again, we will come to them and leaving it at that would be the best goal for a would-be deconverters. I think creating Atheistic art (writing, making movies or YouTube videos, etc.) is a better use of time if someone is interested in deconverting.