I think one of my resolutions for this year had something to do with avoiding idiots. That was way too ambitious a goal. I really should have said avoid arguing with true believers. The core characteristic of the true believer is immunity to evidence. They live in a zone beyond fact and logic.
I was reminded of that **again** - and yes I know that I'm a slow learner - when I continued an email correspondence with a former colleague who likes to paper our local newspaper with letters to the editor criticizing global warming. He made a claim about the last thirteen years of the climate record. I pointed out that his own data didn't really support his claim. He changed the subject to the Vostok ice cores. I pointed out that they didn't really support his argument there either, though they did strongly support the CO2 temperature link. He replied that the end Ordovician cooling (hundreds of millions of years ago) came at a time of high CO2, supporting his argument with a low resolution graph from some right wing blog. There too, further investigation showed that the real story did involve CO2 decrease as well as the movement of Gondwanaland to the neighborhood of the South Pole.
Of course less polite TB just resort to insults and profanity, but changing the subject is a similar strategy.
The best one can hope for from this sort of confrontation is that one might be prompted to learn something - not from your interlocutor - as I learned about the Vostok ice cores and the end Ordovician.
Of course it also decreases whatever faith one might have had in human rationality.