Sat next to a retired oceanographer at dinner last night. Another table companion, on learning his background, asked him if he was interested in participating in the "debates" on global warming in the local paper letters section. He replied that he didn't care to argue with those who didn't care about the data.
That, of course, is precisely the problem with trying to argue with a denialist (the subject of their denial - evolution, nicotine addiction, HIV/AIDS, shape of the Earth - is largely irrelevant). They really don't care what the data says. Their's is an ideology based point of view, not a scientific one.
I once asked one of our string theorist/climate denialist correspondents what facts would convince him of AGW. His answer was interesting - it would take a sudden temperature increase of magnitude that was completely incompatible with the theory and physics of global warming. If confirmation of the predictions of the theory, and contradiction of the obvious alternatives won't persuade, you don't care about the facts - and you aren't worth arguing with.