In our Course on “Terrorism Studies” at the Police Science Institute, we carefully set out that Islam per se is not inherently violent and does not inevitably lead to terrorism, but at the same time, Islam is neither a pacifist religion.
Many other religions have promoted violence throughout the ages, but Islam, in particular, seems to possess all of the necessary ingredients for being violent-prone, or, at least, for following non-democratic methods of conflict resolution.
As part of their dictatorship or theocracy, well over fifty (50) nations in the world support Islam, and, it is the world's second-largest [ twenty (20%)percent ] and is the fastest-growing religion among the oppressed and disenfranchised.
There are no formal “denominations” other than Shiite and Sunni, but all mosques are ostensibly non-denominational, and, it is therefore more accurate to consider schools of thought, sects and/or cults.
Even then, those categories fail to fully capture the richness and depth of Islamic variation since there are "religious" schools of thought (i.e., Sunni and Shiite), "political" schools of thought (chronological and geographical Renaissance periods), "legal" schools of thought (Islamic jurisprudence regarding Koran interpretation), and, the traditional distinctions between sects (i.e., Salifism) and cults (i.e., Qutbism).
It is almost as if the ascetic monotheism in Islam insists that the religion be defined more by opposition than affirmation. Notwithstanding, Islam and Islamic extremism are undeniable social movements to be reckoned with for a long time, as believers think that their prophet, being the last to appear in the Holy Days, makes Him the true messenger of God.
There is however a strong anti-secular thrust in Islam along with a belligerent superiority that make it dangerous, but perhaps no more than puritanical strains in other religions.