In that earlier thread, several folks (correctly) noted that such behavior can be explained by the Dunning-Kruger Effect. While I agree that it explains what they're doing, it still doesn't really explain why they do it or how they are seemingly oblivious to it.
The other day I came across this article....
Overconfidence and Opposition to Scientific Consensus
So to put this in context of my question (why do some exhibit the D-K Effect), the research described in this article indicates that it's due to a combination of factors: lack of humility, one's cultural environment, intuitive-type thinking, conspiracy thinkingThe recent study – Knowledge overconfidence is associated with anti-consensus views on controversial scientific issues, by Nicholas Light et al, is not surprising but is reassuringly solid in its outcome. The researchers compared peoples objective knowledge about various controversial topics (their knowledge of objective facts), with their subjective knowledge (assessment of their own knowledge) and opposition to consensus views. They found a robust effect in which opposition increased as the gap between objective and subjective knowledge increased (see graphs above the fold).
This may remind you of Dunning Kruger – the less people know the more they overestimate their knowledge (although subjective knowledge still decreases, just not as fast as objective knowledge). This is more of a super DK, those who know the least think they know the most. This has been found previously with specific topics – safety of GM food, genetic manipulation, and vaccines and autism. In addition to the super DK effect, this study shows that is correlates well with opposition to scientific consensus.
This study does not fully establish what causes such opposition, just correlates it with a dramatic lack of humility, lack of knowledge, and overestimation of one’s knowledge. There are studies and speculation trying to discern the ultimate causes of this pattern, and they are likely different for different issues. The classic explanation is the knowledge deficit model, that this pattern emerges as a result of lack of objective knowledge. But his model is mostly not true for most topics, although knowledge is still important and can even be dominant with some issues, like GM food. There is also the “cultural cognition” model, which posits that people hold beliefs in line with their culture (including political, social, and religious subcultures). This also is highly relevant for some issues more than others, like rejection of evolutionary science.
Other factors that have been implicated include cognitive style, with intuitive thinkers being more likely to fall into this opposition pattern than analytical thinkers. Intuitive thinking also correlates with another variable, conspiracy thinking, that also correlates with the rejection of consensus. Conspiracy thinking seems to occur in two flavors. There is opportunistic conspiracy thinking in which it seems to be not the driver of the false belief but a reinforcer. But there are also dedicated conspiracy theorists, who will accept any conspiracy, for which conspiracy thinking appears to be the driver.
The topic for debate: Do you agree with that? Do you see this "super D-K" applying to some of the discussions/debates in this forum? Do you think there are other factors the researchers may have missed?
For me, these explanations line up quite well with the behaviors I commonly notice among creationists, most notably the lack of humility. IMO, that explains why creationists are so prone to argue via empty assertion. They think so highly of themselves, they figure "because I say so" is a valid form of argumentation and don't seem to really understand why the rest of us don't.
I suppose such an analytical approach would also rule out the "theory" that humans start out as babies and eventually become adults since you cannot "see" it happen. The lack of humility and profound ignorance that suggests something does not exist if it happens over an extended time period is a wonder to behold. 
