While competent ones tend to underestimate theirs: The Dunning-Kruger effect is "'an example of cognitive bias in which "people reach erroneous conclusions and make unfortunate choices, but their incompetence robs them of the metacognitive ability to realize it'". They therefore suffer an illusory superiority, rating their own ability as above average."
Could this be part of the reason wingnuts are so absolutely certain they're right?

This makes me think of a certain clipper who seems to have a quite inflated belief in their own illusory superiority and loves to claim that others are not intelligent enough to reason properly or to form legitimate opinions.

I think it's a predisposition to the good brawl Lets talk in general, please. And forget old insults, they never deserved. Means of competence, qualifications and achievements are so huge... As in Sarah Palin's example. And, BTW, we cannot perform always and everywhere on the same highest level, because the motivations cannot be always of the same desirability. Or simply bad mood today. And because it's simply impossible. Real masterpieces are rare, unpredictable and not always recognizable at once, as Tchaikovskiy "Swan Lake".