If I understand Islam correctly, which I probably don't, it seems to me that the structure of Islam is such that if things are changing it won't be Islam any more.
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Christianity eventually came around to understanding that the Gospels' anti-Jewish commentary - of which exists much - was a result of still-Judaeo-Christian Christianity coming to terms with still-not-quite-defined post-Temple Judaism. Modern Christianity has made great effort especially after WW2 to fence off this anti-Judaism and to understand what Jews are all about.
If Gabriel Said Reynolds is right, and I think he mostly is, then the Qur'an is (or at least contains) a collection of Arabic sermons from one sect of Christians against (mostly) Catholicism (= Orthodoxy back then). Or - in my opinion - the suras speak for several sects of Christians, and maybe even some Jews, against several other sects, with alliances always shifting. We are, after all, dealing with Near Easterners here
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That would explain the density of polemic. It would also explain sura 5's asides that, whilst there may be some disputes between this sect or that,
at least we can all agree about those damned Jews and polytheists.
-> so, as to what this implies for Islam: Reynolds, at least, is hoping for a reform in Islam which pulls that faith into becoming something more like a school-of-thought within Catholicism. He's been appealing to the Shi'a especially. At least, so I've gathered from his Twitter.
--> Also, I'm not sure that Reynolds will succeed in his aim. What I *am* sure of is that Reynolds is moonlighting. His day-job is scholarship in Islam. He's not a talking-head and he's not a President. Personal politics is fine - like @ssh0les, everyone has some - but politics has/have an inherent danger of infecting one's scholarship.