The way I see it, it is partly because people are heavily biased, and partly because the internet is too difficult a medium to have proper discussions. From what I've heard of the RMAH arguments, most counterpoints are either never considered or ignored when making these arguments. The most popular example of this was people claiming the Inferno brick-wall was a deliberate incentive to shop on the RMAH, despite the fact that the patch notes for 1.0.3 had already been released, which clearly mentioned Blizzard's intention to not only nerf Inferno but increase high ilvl drop rates in lower acts. Another example would be the suggestion that repair costs are a means for facilitating buying better gear on the RMAH, when as stated players now have the option of playing in lower acts to find equivalent gear, and therefore don't need to pay the high repair costs. Also, these points are not as exciting as the conspiracy theory points, and perhaps appear less 'clever' than the conspiracy theory points, giving the illusion to some of being false because they are less intricate (this I feel also is a strong basis for cynicism).