I think you had to see the interview with Laura Koenssberg of the BBC, to appreciate what he was actually advocating, the nuances of his very defensive attitude. He kept quoting Iraq, and suggests that we Talk to ISIS.. Perhaps he would go to Syria and speak to them personally. If he did, would you be thoughtful enough to buy the first bunch of flowers. It's commendable to have principles, but you also have to deal with the real world.
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But in the real world, eventually there will be negotations between the Sunni factions and the Shia. At the moment, IS represent the extreme end of the Sunni revivalism which has been going on, partly in defence against the rise of Shia power (in Iraq), and partly to defeat Assad, and partly to neutralize Iran.
Maybe it's too early for negotiations, but I think calling for them is pretty real, as it was in N. Ireland. And it is very likely that they are going on in the background, not with IS, but with their backers. For example, in Iraq some Sunni tribes have been working with IS, so one task is to peel them away, and it can be done.
Obama knows that the drift to war is remorseless, and he is holding the line at the moment, under severe pressure. But war is a drug. IS want war, some Republicans in the US also, and various right-wing people. So we need sane voices.