Cute theory, but it doesn't really work in practice. If anything, it just makes them want to tell you about Jesus that much more.
The quickest way I've found to shut them up is to not provide them with an audience in the first place.
Everyone is special in their own way, and by "special" I mean the short-bus variety.
"Recognize the phrase 'national interest' as a synonym for 'self-interest' and you will find no moral obstacle that cannot be removed from the highway of ambition."
"The best argument against democracy is a five-minute conversation with the average voter."