Which could be factors that cause people to develop an extremist approach to religion:
If there is only one Godand that one God would not give us many different religions, there can be only one true religion. So all other religions are false.
There exists a believe that the world is a battleground between good (God) and evil forces, Yet many religious people define good and evil by saying that their religion represents the good while all others represent evil. So it is your duty to fight that other religion. This must be God’s will, and it is only for the salvation of non-believers.
If a religion is given by an almighty God, its teachings and doctrines must be absolute and infallible. Again, it follows that all different beliefs must be partly or wholly erroneous.
God is perfect and thus a doctrine given by God must be perfect. This only religion provides not only an infallible description of God, but is also complete. Something which is perfect could not possibly change, even never evolve or change over time.
There is no need to adapt a religion to changing times—instead the times should adapt to the complete and infallible doctrine. In other words, the believers must resist all changes in their religion.
If religion must be defined in terms of black and white, then one religion is completely right, while all conflicting religions are completely wrong. There is no possibility of a compromise, because if you give the Devil one finger, he will take the whole hand.
There is only one way to interpret the religious scriptures. Obviously, it is the interpretation chosen by the current church leaders. All other interpretations are wrong and come from the Devil. Therefore, it is a duty to eradicate such false interpretations and possibly even the people who promote them.
The leaders of their religion are God’s representatives on Earth. The leaders speak for God and therefore they should never be questioned or gain said. Blind obedience is demanded and thus anyone who does not respect this absolute authority is seen as an enemy.
Human beings have always had a tendency to avoid taking personal responsibility for their own situation, all problems are caused by other people. This leads to the belief that all of the problems in the world are caused by people who belong to false religions. Non-believers then become the scapegoats. In other words, anyone who disagrees with or opposes your beliefs is deceived by the Devil or working for the Devil.
Many religious people believe their religion represents the ultimate cause. They are fighting for a just cause, backed by the ultimate authority, namely God. Therefore, everything they believe or do is right in an ultimate sense. This then makes it possible for these people to justify almost anything as being necessary in order to win the ultimate victory.
The sense of ultimate justification easily leads to the sense that the ends can justify the means—any means. Some people believe that because they are working for God’s purposes, it is acceptable to violate the laws of God defined by their religion. In other words, it becomes acceptable to kill other people in the name of God even though virtually every religion defines killing as wrong.