Omar Ali in Brown Pundits:
Someone then commented (and I urge you to read the post and the comments, and the hyperlinks, they are all relevant and make this post clearer) as follows:
“Well, if you take the Old Testament and Koran at face value, the OT is more violent. The interesting question is then why Islam ends up being more violent than Judaism or Christianity, and for that I agree you have to thank subsequent tradition and reinterpretation of the violence in the text. It appears that for whatever reason Islam has carried out less of this kind of reinterpretation, so what was originally a less violent founding text ends up causing more violence because it is being interpreted much more literally.”
I replied there, and then thought I would put that reply up as a new post here because I want to see what people think of this quick and off-the-cuff comment. THEN, I can maybe improve it in a final new post this weekend. So, without further ado, my comment:
There is an easier explanation. Islam the religion we know today (classical Islam of the four Sunni schools and it's Shia counterparts) developed in the womb of the Arab empire. It is evident that it provided a unifying ideology and a theological justification for that empire (and in the case of various Shia sects, varying degrees of resistance or revolt against that empire), but at the very least, they grew and formed together; one was not the later product of the fully formed other. Being the religion of a (very successful and impressive) imperialist project, it's “official” mature Sunni version obviously has a military-supremacist feel to it.
More here.