So, how does it happen that apparently intelligent people fail to follow basic sound intellectual processes to come to obvious conclusions?

Well, I think politics and profit play a part.  No doubt there are also human beings out there whose intellectual processes get shut down by emotion and fear and these fragile souls are so unnerved by the fear of an impending terrorist attacking them that all higher brain function shuts down and simple equations cannot be solved.  There is only fear and plenty of fear mongers to play on that fear to sell plastic sheeting, duct tape and worse.

But I think there is also some element of evolutionary neurological function at work in these abject intellectual failures.  Human beings evolved to sense imminent danger (sorry, I think Darwin’s theory of natural selection makes more sense than the 6,000 year old earth creation theory).

We are spooked by things that might be moving in the dark near us.  We evolved with a neurological system that has been honed by natural selection.  A neurological system that was a little slow at spotting a hungry predator became lunch instead of a parent.

Our neurological system did not need to evolve in a way that would recognize slow moving threats.

Be patient, we are getting close to the frog’s eye and what it tells the frog’s brain.