One major obstacle to rational thinking is a phenomenon, which has been called "book authority". It is a philosophical method in which an argument is proven by reference to a written source that enjoys ultimate authority over a topic.
The most obvious example are religious scriptures. They are supposed to be of divine origin and therefore enjoy a higher authority than any other form of human epistemology including rationalism or empiricism. This means a believer would rather trust a scripture than his own logical conclusions or personal experience.
People with Western secular education usually believe to be free from such methodical fallacies, but this is unfortunately not the case.
I'd like to recount at this occasion a recent experience that I had during a discussion with a friend. This friend of mine is not particular religious and has a full Western school education, so he should actually have been familiar with the scientific method.
During a conversation about the tides of the sea level, he made the statement that the tides would shift daily for a length of 25 minutes. This means high tide would be every day 25 minutes later than the day before. I quickly calculated this number and came to the conclusion that the time shift had to be about double the time. However he insisted that it was 25 minutes, because he had read this number somewhere.
So I demonstrated him by an easy calculation that this could not be true:
The tides are caused by the moon. The moon orbits Earth in about 29 days and one day has 24 hours. Therefore the time shift had to be 24h/29 days = 50min/day.
My friend did still not agree.
He was fully aware that the tides are caused by the moon, that a moon cycle has 29 days and that every day has 24 hours, but he was still not willing to accept the validity of this simple calculation just because he had read a different value somewhere. This means he was willing to accept that 24h/29 days = 25min/day just because it was written in some unknown book and although it contradicts a simple mathematical calculation. that he could easily do himself. He had given "book authority" priority over his own ability to calculate.
His belief in "book authority" was even more obvious, when he later asked me to back up my claim by a link from the Internet. So he was willing to accept another "book authority", but unwilling to give up his false belief just based on logic and mathematics.
Unfortunately we have a lot of people acting this way. They want a written proof, and be it an article from Wikipedia, in oder to believe something. Logical reasoning is not enough for them.
I have also made similar experiences during discussions with other scientists. Even if somebody just makes a logical conclusion, they ask for a source for it. Providing references and sources has become an obsession. It is almost like scholastic theology in the Middle Ages. You need to back up everything with a quote from the bible. Famous scientists like Einstein or Hawkins are quoted as some kind of divine authority. If Einstein said so, it has to be true, even if it is beyond our understanding, because he is supposed to have had some sort of supernatural inspiration about how the universe works.
This way of thinking has nothing to do with the scientific method. It is not rational. It is some kind of outsourcing of thinking. For some reason, be it laziness or lack of self-confidence, people are unwilling to think for themselves. So they let others think for them, trusting fully in their authority on the subject.
Well, if you want to outsource your thinking, you better have some very competent authorities. Unfortunately this is often not the case because these authorities may have their own agenda, which might not be finding out the truth or letting you find out the truth.
Our own ability to reason and logic should always be the highest authority, not some person or some books.
But the most problematic issue is that most people are not even aware, when they put their trust in "book authority" instead of reason and logic. Observe yourself next time when you look up something in Wikipedia in order to decide an argument that you just had. Are you just putting all your trust into a guy, because he has an academic title, or a book from a respectable publisher or are you really able to understand what is told and is it in accordance with your own observations and rational conclusions?