Denialists... They come in many forms: HIV-AIDS deniers, Global Warming deniers, Germ Theory deniers, Gravity deniers, Evolution deniers(usu called I[ntelligent]D[esign]iots or Creationists), name any scientific concept and you'll find one who doubts its validity.

It's a wonder why, despite overwhelming contrary evidence, that they manage to hold on to their beliefs. I blame the neglect of history. These denialists usually claim that this certain study done before gave results that are contrary to mainstream belief or that in the past, this theory was believed to be true and the reason we don't consider it now is because of politics. They also believe in things that were already disproved and seem to be really ignorant about the fact that is was disproved already. Atleast, nobody denies that we have hearts...

I think if they just studied their history and read about all those experiments that scientists performed to prove or disprove something, maybe, they'll be a bit more quiet. IF they really read about how scientists(especially during the late 1800's and early 1900's) are trying very hard to not lose face and gain eternal glory just to prove their hypothesis and how heated these series of debates and experiments became, they'd probably understand why the scientific method works and why we have these facts and scientific truths. Maybe they'll even pick up why they are wrong in believing these forgotten theories and realize that politics played a very small role in science.

Then again, a huge part is their distrust of people or at least those in/with power or the knowledge. Not that it's such a bad thing, many important scientific discoveries were made due to this distrust(Galileo for instance) but it distrust can only be up to a certain degree. Distrust of something many have proved to be true and trustworthy without explaining why you distrust it(like those who distrust the scientific method) is crazy. Many of these denialists like to think themselves as those who branch off from the thought of the mainstream, as a certain kind of noble rebel and probably aspire to be the next Galileo, unfortunately, most of them are just full of hot air and are miseducated about the things they "rebel" against.