The root cause of extremism is intolerance, a self-engaging exaggeration of the incapacity to respect or tolerate the ways of others. It is a tendency to see oneself as above others, thus drawing on animosity and hostility toward those who view things differently.
Religious intolerance is bred from such views. Religious fanatics assume the high ground for supremacy and the "preservation" of morals. These religious groups tend to misappropriate divine context and manipulate interpretation of religious traditions, doctrines and sources in order to serve their agenda. They tend to uphold a puritanical and literalist interpretation of divine texts to suit their warped ideology and purpose.
The minds of extremists like bin Laden think they are justified in attacking others that oppose their ideology. Muslim extremists think along the same lines but they have erroneously sidelined the Koranic message that no formal religion can exclusively claim right of salvation. (Koran, 2:62)
Since God intentionally created human diversity and bestowed dignity on humankind, thus His mercy extends to all who strive in the pursuit of virtue:
"To each of you God has prescribed a law and a way. If God would have willed, He would have made you a single people. But God's purpose is to test you in what he has given each of you, so strive in the pursuit of virtue, and know that you will all return to God, and He will resolve all the matters in which you disagree." (Koran, 5:48)
Islam calls for Muslims to be respectful and moderate in every aspect in their life.
The Prophet Muhammad called for a path of living life in moderation and not excessiveness. He even warned that "extremist fanatics are doomed."