I don't think Western politicians, especially US ones, have never understood the Arab/Muslim mentality, especially loyalty to their religion.
Which is why Cameron stood up and said we won't stop until ISIL's poisonous ideology is defeated. I may being a little pedantic, but you cannot defeat an ideology. You can counter it and restrict its opportunities to grow and flourish, but defeat it, no, not militarily. That's why the King of Jordan in an interview last year characterised this as WW3 in all but name; he rightly noted that the current military action can only ever be the short term solution to remove the perpetrators and buy time for the politicians to set the conditions for the longer term generational aspects of the struggle. And as for the generals and politicians putting a 3 year timeframe on this (or however long they said last year), they would do well to remember John Reid's notorious 'without a shot being fired' statement. This is way longer than a 3 year job if you're going to do it properly and not just suppress the problem temporarily as we did with AQ-I in the first place.
Unfortunately that's what was supposed to happen in Afghanistan as well; how did that turn out. Let us hope the wise beards amongst the Jordanian government and tribes react in a decisive but clinical manner. Two executions of already convicted terrorists will never be enough, there will be more to this. But I hope it will be surgical rather than feeding the beast by simply lashing out, although that would probably feel far more satisfying at the time.
As for der Spiegel, last week they had a fill scale investigation in to Syria building a nuclear plant in secret on the Lebanese border. I wouldn't take what they say at face value without doing a bit of checking first.