Living in the bible belt I've had the door-to-door religious folks stop by occasionally, and I do openly and politely discuss with them how their belief systems are wrong. It's fun when they try and explain the flaws of evolutionary theory, and how it is "just a theory". Even more fun that one thinks he knows what he's talking about, but you can see the seeds of doubt rise in the eyes of the secondary as you explain the simple facts of evolution, a system you can recognize in your day-to-day rather than some system of faith. They all give up at some point when it becomes obvious that I know more on the subject than they do, though they will leave pseudo-scientific pamphlets on matters like UFOs (seriously). Needless to say, I don't get a lot of repeat visits though they all promise to come back once they've "researched" the answers. I usually give them an out in that faith in science does not preclude the existance of a higher order, and that faith is a personal experience which can't be shared. I wonder if any of them are converted.