Although I will be referring to Muslims because the actions of some Muslims are in the current news, let us not forget that other believers have taken drastic action. The Grand Inquisitor, Torquemada, had many tortured and killed because they were suspected of not having complete fealty to the Church of Rome. The Puritans of Massachusetts executed Quakers because they refused to stop preaching. And the Jews of Biblical times slaughtered those who worshiped Baal.
The latest incident to make the news is the assassination of the Governor of Punjab by one of his bodyguards. The "sin" of the Governor? He wanted to overturn the blasphemy laws of Pakistan that call for the death penalty for those who "insult" Mohammed or Islam.
Other incidents include the murder of a Dutch filmmaker and the threats against European cartoonists who have "insulted" Mohammed or Islam.
If God/Allah is omnipotent, wouldn't God/Allah deal with blasphemers with a bolt of lightning or other public displays of power? If Elijah's Jehovah could burn a water-soaked offering pyre, why did Elijah chase down and kill the priests of Baal?
If God/Allah is unknowable, how does anybody know the mind of God/Allah enough to actually carry out "God's will"? If a person assumes that he knows the mind of God/Allah, isn't that blasphemy too?
It is ironic that many Muslims preface taking an action with "Insallah" ("God willing"). But if they don't know God's will, how can they act in God's name?
I think people who attack those who believe differently are themselves insecure in their faith. Their beliefs are threatened by those who believe differently. This holds for radical Muslims, the Puritans, Torquemada, or Elijah.
Fortunately for those of us who don't have the "True Belief", whichever one that is, most of the co-religionists of the "True Believers" are willing to get along with others who do not share their beliefs.