Irrational faith is based on abduction: You see something that matches your experience and draw conclusions based on similarity alone.
Rational faith is based on induction – and mind you, this is where we base most of our cognition. Deduction requires that we know all the premises involved, and this we seldom do. With induction you recognise that you know only some of the premises involved and you venture to draw a provisional conclusion. However, every time this provisional conclusion seems to match your personal experience, the stronger you faith becomes, all the way knowing that this certainty is subjective and does not put anybody else under any obligation.
And this is where we have the problem: People believe that their personal subjective certainty gives them the right to force others to follow their ideology (by means of legislation and otherwise). Please notice that I am not speaking of religious faith only. This subjective certainty is found in all areas of life such as in economics and politics. When people lose faith in the American dollar crisis is knocking at the door.
About fanaticism: This is a value-laden word you apply on people who wholeheartedly support a course you do not agree with, especially if you feel that they have based their personal certainty on abduction.
Do not fear people who know that they believe. Fear those who believe that they know!