Donn
Philosopher
No amount of appeal to straightforward reasoning like lack failure of clinical trials, failure to submit claims for million dollar prize, etc. will have any effect on the believers views as the facts are easily countered when one has a non-Occam's razor type view of the world.
I would imagine you know more about this than I, but I am new at this dance.
What if one got hold of a particular view and boiled it down to its essence; eliminated the chaff and reduced it to as stark and basic a set of issues as possible; and then attempt to demonstrate with examples and maybe even home-experiments that the science of the thing shows X and they think it shows Y?
I tried this with the Blue Mars questions, trying to argue from a light wavelength, absorption pov but I could not get enough good info from boards like this one or Bad Astronomy to do so, mainly because they argue that there just is not enough evidence yet - so lack of ability on my part is a problem - but the stategy should be sound: Hone-in, pose the problem, demonstrate the elements of it and how it resolves and then ask them to place weight on their now very shakey leg.
One should simply pick one's areas of focus more carefully; ensure a fighting-chance!