Having been in retail for 20 years the more a customer is in the wrong (i.e they did something stupid themselves) the louder they shouted the odds. In fact an overly aggressive customer always makes me suspicious. Not a great deal you can do about it though.
The emperor's new clothes is also relevant here. It's also why objectivity is so rare in all Irish walks of life. It's inherent in any "anti-intellectual" culture.
I try to be disinterested (look it up) in decision making processes where I want the best outcome but am open as to what that is. Maybe it's a light ego , maybe it's a scientific background, but all I know is that sometimes it's misinterptrted as being "weak or indecisive.
It appears that the true believers feel safer in numbers, and they're often finding validation in their beliefs, not in the content of their beliefs or the evidence or the merits of what they believe in, but in re-assurance from others that their beliefs are reasonable.
One would think that this would lead them to switch to the more popular belief system, but this would be to admit failure, that the beliefs they previously had were wrong or that someone else was able to have unrequested influence over them, instead the strategy is to try and convince others to switch to their side.
There are a lot of psychological barriers out there where the true believers can be very difficult to reason with. One particularly frustrating element is that the human brain appears to be good at remembering statements, but very poor at remembering value judgements.
ie, whether the statement was true or false
Eg, If you read "Politician cleared of corruption charges" your brain will only remember the politician and corruption charges bits, and will be unsure what the link is. If you're already pre-disposed to dislike that particular politician, you'll remember the story as "politician charged with corruption".
If you have an entrenched position, you can be presented with some extremely powerful evidence that shows your position is flawed, but you will subconsciously filter a lot of that information out and only select those bits of information that you think supports your own position.
As far as practical strategies for dealing with people like this, I suppose, teaching people critical thinking skills through engaging with them and pointing out the logical fallacies that they are engaging in is a start.
Pointing out that all the genuinely skeptical organisations and experts in the field all tend to have reached a different conclusion to them, and they are left with siding with professional PR companies, vested interests and quacks for political academic and scientific support.
Then pointing out that claiming that all the skeptics are all part of the conspiracy is not a very convincing argument....