As people mature they develop a world view, or ideology, about how the world "works". It doesn't really matter whether the ideology is true, factual, provable or even shared by others, but these factors do come into play. When confronted with something that doesn't conform to their world view people don't alter their ideology, they deny the facts. A few examples:
The world view -- President Obama isn't a natural born citizen. The facts -- there's a birth certificate attested to by the state of Hawaii. The denial -- it's not a birth certificate, it's Photoshoped, the typing fonts are suspect, etc. A recent poll shows roughly 50% of voters of identify themselves as Republican still have doubts about President Obama's citizenship.
The world view -- the End of Times and the Rapture were supposed to happen this past weekend. The facts -- it didn't. The denial -- God has given us more time to atone, who cannot truly understand how the deity works, a fallible human misunderstood God's message and the end time is now coming in 20XX, etc. Sociological studies have concluded that people who believe in apocalyptic scenarios actually increase their spiritual commitment after the apocalypse date has passed.
Now are these ideological driven people non-intelligent? Of course not. Whether the topic is climate change, capital punishment, gun ownership, recreational drug use, evolution, capitalism and democracy, vegetarianism or religion, intelligent people seem to have widely diverging and frequently polar opposite opinions.
In the audiophile world it plays out along these line:
The world view -- if it measures well, it will sound good. The facts -- some well speced products sound like shit, some poorly speced products sound real good. The denial -- You're not measuring the right parameters, you don't know what accurate sound is/you like the sound of distortion, your measurement techniques are faulty, etc.
The world view -- I only trust my ears. The facts -- standard scientific tests have repeatedly demonstrated how variable and how easily fooled human senses are. The denial -- science doesn't know everything, I hear a difference, your system isn't revealing enough to show the difference, double blind tests don't work, etc.
We all need a world view/ideology to make sense of what would otherwise be a bewildering, indecipherable series of unrelated events. At the same time that world view blind us and prevents us front looking at information in an unbiased manner.