"... there will not be any peace...until the different sides of the Islamic divide devise a means of tolerating each other?"

Rather like the many sides of the "Christian"[sic] divide, innit?

Yes, actually. Different varieties of Christians may not always get on too well, but the days when we had wars of religion about such things, and had public executions have receded into the past.

There is nothing that Isis does which hasn't got parallels with things that our Christian ancestors used to do to each other a few centuries ago.