I am a fan of Dan Carlin's podcasts, especially his show Hardcore History (a terrible name for a show, but an excellent podcast nonetheless). The most recent episode, as of the time that I write this, is about the Anabaptist rebellion in/occupation of Munster, Germany in 1534-1535.
If you are interested in this historic episode, I strongly recommend that you listen to the episode (just click the link above). But the thumbnail is this: The Anabaptists were one of the early Protestant sects that arose after Martin Luther posted his list of theses. They were far more radical than Luther himself was, and the Anabaptists gave rise to numerous sub-cultures, including several that were essentially communistic doomsday cults (yep, history is often weirder than fiction). One such group became violent, and established a short-lived government in the German city of Munster, where they managed to hold off the local authorities for a time, while establishing a miniature totalitarian theocracy within the city itself. They were eventually crushed by the city's Bishop (a secular as well as religious authority figure at this time in Munster), and the leaders of the rebellion put to death in a rather horrific manner (though one that won't surprise students of Medieval history).
This story has echoes throughout Europe. In England, Protestant sects gained power under Oliver Cromwell, and established an authoritarian theocracy in England (though, to be fair, many would have considered the deposed-then-executed Charles I's monarchy to be authoritarian as well, and arguably also a theocracy as Charles I was also the head of the Church of England), and then near-genocidal campaigns against Catholics in Scotland and Ireland. Under Oliver Cromwell (the Lord Protector, a role different than, though in ways comparable to, the king), England became hostile to things such as drama, dancing, etc. In fact, the attitude of the government under Cromwell towards the arts and entertainments is rather reminiscent of Afghanistan under the Taliban**.
Comparable stories played out across Europe, with Protestant sects rising, and committing acts of violence, including ones that we would now consider terrorism in England, France, the Netherlands, Germany, Italy, and on and on and on.
These stories fascinated me, but they do not surprise me. They might, however, surprise many contemporary people in the United States.
There is a commonly held belief here in the U.S. that Middle Eastern violence and world-wide terrorism is a product of beliefs and ideals unique to Islam. Islam, this belief holds, is unusual among the Abrahamic religions* in its advocation of violence. Therefore, it is the only of these three religions that produces violence on the strength of the religion itself. Sure, there have been evil/violent people who claimed to be Christian or Jewish, but they just used religion as an excuse to do what they were going to do anyway. Islam actually causes the violence!
People who hold this opinion are thoroughly ignorant of history.
In part, the ignorance is willful. People rarely want to acknowledge that the club to which they claim membership can produce bad seeds. As a result, Christians tend to deny the role of religion in the European wars of the 16th through 18th centuries, but they are hardly alone. Members of most ideologies that have produced violence tend to deny that the ideology produced said violence.
In part, it's the fault of those of us who deal with the past professionally. We have a hard time grappling with ideology, and as a result, tend to look for other causes for violence, when ideology may be the cause. As is summed up by historian R. J. Knecht in his book The French Wars of Religion, 1559-1598:
Many people nowadays attach little importance to religion. Consequently, they find it difficult to believe that it played a major part in the civil wars that tore France apart in the late sixteenth century. They look for other reasons: political, economic and social. Religion, they argue, was merely a 'cloak' used by the great aristocratic families to give respectability to their ruthless pursuit of power. But the sixteenth century was not the twentieth: religion did rule the lives of thinking people...
...even today religion can move people to action, as is daily demonstrated in the Middle East and India...Material interests, including brutal power-hunger and greed, were certainly present in the French Wars of Religion, but religion was also crucially important.
Although Knecht focuses on religion, it is not unique. Any sort of totalizing ideology - a belief system that claims to encompass either everything, or at least everything that matters for living in the world - is capable of producing the zealotry and hysteria necessary to create violence. Religious violence is nothing new, likely having been with us from a very early in our time in our history as a species, but is has at times been joined by other ideologies as a source of violence - witness the anarchist bombings of the 19th and early 20th centuries, for example.
We know that Christianity is capable of the same types of violence as modern militant Islam not because Christianity shares many ideological underpinnings with Islam (though it does), but because Christianity has produced precisely the same sort of sectarian violence, political and social oppression, and acts of terrorism in the past. Christianity still has the potential, and a theocratic undercurrent still breathes and seethes and seeks power (look up the Dominionist movements). The story that we often hear is that Christianity gave rise to the Enlightenment (or, if the commentator dislikes the science and necessity of doubt that came with the Enlightenment, they will try to claim that Christianity is the source of the parts of the Enlightenment that the commentator likes). The truth, though, is that Christianity was muzzled by commerce and politics, beginning in the Netherlands during the Renaissance, where city officials and business interests realized that persecution of religious minorities could be bad for profits. The more peaceful Christianity that we know today is a product of historic de-fanging, a religion that has been molded by social currents and mores, as much as (if not more than) it has influenced the social currents and mores.
The rise of ideological authoritarian states has happened many times before...and it sure as hell will happen again. While religion is typically the cause (being the most common potentially authoritarian ideology among humans), it can also occur with non-religious ideologies (noteworthy 20th Century examples include Nazi Germany, the rise of the U.S.S.R., and Cambodia under Pol Pot). Similarly, the rise of ideological violence and terrorism is also nothing new. Essentially, all that is required is for some group to conclude that they know they absolute truth, and believe that they, therefore, have the right to impose that truth on everyone else.
But we need to not be ignorant of history. We need to acknowledge that while the technologies and means used by ideological zealots may change, their presence seems a constant. We need to acknowledge that our own religions and political ideologies could, potentially, lead to chaos and violence - in part we need to acknowledge this to keep ourselves humble and not demonize our opponents, and in part we need to do so in order to prevent our own creeds from becoming the enemies that we loathe.
*Worth noting: many people who hold this belief would leave out the Abrahamic religion part, as many people who believe this are so thoroughly ignorant of Islam that they are unaware that it shares a good deal with Judaism and Christianity.
**Monty Python produced a funny and informative song about the English civil war:
...or, if you have a bit of a different set of tastes, I will happily recommend Mark Steele's version to you:
***Though I would note that their own actions were a result of the overall form of communism to which they adhered, where atheism was a part, but not in any way the whole. In much the same way, while most people are loathe to admit it, Protestant Christianity (specifically Lutheranism) was a part of Nazism, but it was in no way the whole of Nazism.