"Tarl:" I love it that, when asked about comparable violence by other religions, the most Islamist sympathizers like you can muster is over 600 years ago during the Crusades, and the IRA, which hasn't had a scale attack like this in over 21 years.
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The leaders of ISIS, Al Qaeda, etc. all have postgraduate and Doctorate degrees in Islamic studies and theology: they know more about Islam and its teachings than you ever will, and have committed most of their holy works to memory: believe me when I tell you that you have no place calling their religion- which they live and know more about than you do- a "perversion."  They do what they do explicitly because of their religion-  Oh, they can't do that?  Guess what- they just did.
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Fin Shen and Christian sects learned, grew, and evolved: why won't Islam?