It's an interesting idea, but I have no idea how to determine how effective it might be.Pointing out to people that if they live like secular humanists they may actually be... That is very gutsy. Possibly that is what people need. I could see printing up some tracts and passing them out. It could be revolutionary if done right and seriously. I don't think anyone has ever done it.
I am a great believer in "holding up the mirror" when I think that people are being inauthentic -- especially when they are probably unaware of it themselves. But I am also aware that people very often see what they want to see, and can be spectacularly poor at seeing the mote in their own eye.
It's funny, but Mark Twain wrote some quite funny stuff in a piece called "Letters From the Earth." These letters are from Satan, back to his fellow angels, and describe the strangeness of this creature called "man." It's worth have a look-see.