From the article:
The study involves individuals with radical political beliefs, as measured by a standard questionnaire. It has already been established that those with more extreme beliefs espouse greater confidence in their knowledge and beliefs. However, it is not clear how much this is due to an overconfidence bias vs a failure of metacognition. In other words – do people who are overconfident about their political beliefs like to portray themselves to others as being confident, or do they simply lack insight into the correctness of their own beliefs (a metacognitive failure). The current study tests the latter factor.
This is only one study, but it’s an interesting one. It basically says those with radical political believes don’t really identify when they are wrong. They stubbornly adhere to ideas when they are clearly in error. This, according to the study, is probably a metacognitive failure for these people.
I, like the author of the article, am more inclined this failure of metacognition is an outcome of adopting radical ideology, and the necessary mental hoops needed to keep it, but that those with a tendency towards metacognition failure are the ones that do it most.
Simply put, this is why your racist conspiracy theory Uncle at the Christmas table will argue the sky is not blue at every turn, no matter the evidence to the contrary.