I find religious fanatics scary and infuriatingly self righteous, but words usually fail me on this subject. Luckily  there are other people who can say so well what should be said a lot more often and a lot more loudly in order to protect the good things on earth from these destructive, angry followers of their ‘righteous’ gods.

And here is a pretty good short summary, written by John Firman and Ann Gila, on religious fanticism:
Our world today is torn asunder by men and women who claim that God is on their side, and who,secure in the righteousness of their positions, perpetrate acts of violent destruction. Such individuals are driven by the certainty that they are privy to sacred truths and are therefore morally obligated to do everything in their power—no matter how many people may suffer—to act upon these truths. Coupled with their inflated sense of personal rectitude, moral certainty, and ideological purity is a tendency to dehumanize and even demonize those who oppose them.
Although this disorder can be called “religious fanaticism,” those afflicted need not appear wild-eyed or deranged; quite the contrary, they can present themselves as thoughtful and responsible people inspired by the loftiest of ideals. Nevertheless, their absolute confidence in themselves and their cause, their willingness to create massive destruction for a supposed higher good, and their dehumanization of their opponents, all indicate the imbalance of a personality disorder. We need not point out specific examples of this disorder perhaps, except to say that it can afflict anyone, from the person on the street, to the international terrorist, to the leader of the most powerful nation on earth.