Hate to break it to you, but the use of religion as a reason for war is pretty much a problem of the Jewish descended religions. Not exclusive mind you, but if you look at wars where the primary reasons include religion you won't find many that are not part of the Jewish/Christian/Islam set.

It's also important to remember that many wars that had religion as the claimed reason really had little to do with religion. Several of the Crusades for instance had far more to do with land, money and politics then religion, though religion was the reason given for all of them.

There are a couple of reasons for why wars and Jewish descended religions are tied, but the key one is the built in idea of having a exclusively correct view of reality. This causes problems not only for the overt problem of forced conversion but also because it makes it far easier to weld a group of people into a single large force and it makes it very difficult for any of these religions to share a population with another religion.

As for why Islamic fundamentalists? Once again, there are number of interlocking reasons, but the two key ones are the total belief that they are right and the inherent violence of Islam.

The first is the same one I gave above, the inherent idea in these religions that they have an exclusively correct view of the world. Because of this they see no problem forcing their beliefs on others. And this is by no means exclusive to Islam, Christian and Jewish fundamentalists are just as bad. Christians fundamentalists are always trying to force their view on others while at the same time trying to keep from being exposed to any other ideas. It's the same psychology, just using different phrasing.

The second problem is that Islam takes the Judo-Christian glorifying of war and turns it into a religious imperative. Muslims are told they have a duty to spread the faith, and that war is often the preferable way to spread it. Thus it should come as no surprise that Muslims fanatics resort of violence to achieve their goals.

Jay