"Islam was spread through violence and it continues to spread through violence."
My theory, greatly simplified to fit the space:
Islam started at a time in history where there was a lot of turmoil and "disorganization". Violence was relatively common. Most current religions have had violence involved in their history to some extent. The difference is that most civilisations and religions moved away from violent tendendcies in favor of intellectual development. In these societies, those that were violent were either executed, punished or exiled. Some forms of violence persisted longer in areas of many civilisations, but, for the most part, civilised societies developed to the point where violence is not generally accepted.
Islam, however, has regressed. Muslims look at violence as a virtue. Those with the most violent characteristics and the most hair-trigger flight-or-flight-responses are considered the strongest, are emulated and are made leaders, both civic and religious. Over the centuries, Islam has become more violent because anyone born into Islam who showed peaceful tendencies was considered a traitor to be outcast or murdered. The most violent became the most powerful and wealthiest, and, consequently, had the most wives who produced offspring with tendencies towards violence. Thus, the violence in muslims from the core of Islam's beginnings has a gentic component. Islam has been able to jump to non-Arab cultures by attracting the violent subcultures in remote areas. In this way they have been able to leap into distant parts of the world and sow the seeds of violence and terror. Islam has become expert in terrorizing. Muslims attack and murder nonmuslims. Then they get off of the hook by claiming that they were being discriminated against or harrassed, that they are a poor, peaceful minority. And muslims are very successful because they are usually attacking truly peaceful people who are unarmed. Once there are sufficient muslims in an area, many of the remaining residents capitulate to Islam and convert. This continues until there is a muslim majority. Once that is acheived, all other religions may just as well leave the area or they will face a tortuous existence.
Virtually every country that has attained a muslim majority shows the true face of Islam: Intollerance of any other religion and rampant violence.
Reminds me of the old saw about how the CIA predicted who would be the next premier of the Soviet Union. They picked two candidates from the possibilities: one was the stupidest of them all, the other the most brutal. One of those two would win.