Honestly mate I'm not sure you would. I watched some debate thing on youtube and decided I'd end up punching them for being so stupid. Basically they just dismiss any of the scientific reasons for their claim being ludicrous - its a conspiracy, that science is made up etc etc. I can't get my head round how you get to that point in life. Its one thing believing that there is loads of dodgy stuff going on in the world secretly, or UFO's etc. Its quite another to believe that the earth is flat.
when passenger higher atmosphere space travel is up and running we should just send up these ****s to have a look for themselves. They will have some illogical explanation for what their eyes see too I suppose.