My own board was recently killed by one, nothing could be posted without him/her butting in and everyone expended so much energy responding that they finally just got sick of it and stopped posting.
Whats with that, anyways? I'm pretty sure an Atheist troll on a Christian message board would just be booted with no second thought. Why indulge them? I'm not saying kick them off, but why respond when you know they're just here to try to convert you?