Islam

A religion of peace:

Jihad is your duty under any ruler, be he godly or wicked.
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A day and a night of fighting on the frontier is better than a month of fasting and prayer.
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The nip of an ant hurts a martyr more than the thrust of a weapon, for these are more welcome to him than sweet, cold water on a hot summer day.
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He who dies without having taken part in a campaign dies in a kind of unbelief.
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God marvels at people [those to whom Islam is brought by conquest] who are dragged to Paradise in chains.
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Learn to shoot, for the space between the mark and the archer is one of the gardens of Paradise.

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Paradise is in the shadow of swords.

These are from the hadiths, as noted by Bernard Lewis in his book The Crisis of Islam: Holy War and Unholy Terror. Now, that isn't to say that Islam is a religion of war or violence. I think Islam, like most religions, is whatever its believers and leaders think it is, which tends to change over time. Christianity was used to justify the Crusades, but is also the basis for numerous charitable organizations who perform work all over the world.

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The point is: let's not kid ourselves that Islam is automatically a peaceful religion that could easily be confused with Buddhism. It's followers could be violent. They could also be peaceful. It all depends. Indeed, Lewis also points out the following from the hadiths:

Be advised to treat prisoners well.
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Looting is no more lawful than carrion.
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God has forbidden the killing of women and children.
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Muslims are bound by their agreements, provided these are lawful.

Plainly Zarqawi and his followers are in violation of at least two of those provisions. The problem isn't with Islam, but the people who have much of the influence over it. That they preach violence should not be a surprise -- look at the symbol on this flag.