I asked for this so I figured I needed to respond even if it is a few pages stale.
Eric Rudolph and Timothy McVeigh and a whole bunch of other fat comfortable christian Americans who think that god has charged them a righteous crusade against the unholy heathens would like to tell you some good news. and the 5-7000 ISIS fighters that made the reverse migration would like to share some good news too.
You place a religious conservative family from Syria into a liberal secular European country and what do you think will happen when their daughters/sisters start coming home with local boys, dressing "like a slut" and listening to that devil music. This western temptation is corrupting or youth! They will see, "oh the west really is against god. it really is a plague of degeneracy on the world that needs to be wiped out" it happens with Christians in America, why wouldn't it happen with Muslims in Europe?
Saudia Arabia, Iran, the UAE, and Jordan don't have huge problems with domestic terrorism are all also totalitarian theocracies that will eagerly crack your skull at the slightest sight of not fervently praising the national government
You cannot have terrorism without an ideology that pushes you to sacrifice your life for a greater good. You can have that if you have nothing or if you live in the lap of luxury. If you feel like you are better and have absolute truth and the rest of the world just needs to fall in line. Religion fills this role wonderfully, in fact that might be it's purpose, to give a uniformity of thought in a population and to make that population willing to serve the greater good. Why do you think there is always a war on Christmas?
and then there is the bigger question of maybe they are right to a degree, maybe islam and western liberalism are incompatible after all.
I'm pretty sure I stated in one of the dozen posts I made in this thread that yes, you're going to get terrorists even in a comfortable, well-off population, but you're not going to get large scale movements like IS or Al-Qaeda. You'll notice that all the people who left European counties to join IS... left their countries. They didn't stay to fight at home, they went to Syria.
What you describe probably happens, but then again, I suspect that Muslims who really do think the West in the devil, or immoral, and that western values will corrupt their youth won't choose a western country to come to. They'll go to Turkey, or Lebanon, or Jordan, or Saudi Arabia, or Egypt. Do remember that far, far more Syrian refugees have gone to other Middle-Eastern countries than have gone to Europe.
Of the four countries listed, only Iran is a theocracy. The other three objectively are not. Jordan is actually a fairly liberal secular constitutional monarchy (relative to other states in the ME), and is probably one of the greatest success stories of the Middle-East.
You cannot have large-scale terrorism without circumstances that favor the creation of large paramilitary movements specifically focused towards committing criminal acts for political ends. Those circumstances almost always (as in I can't think of a case where they did not) involve perceived oppression, stemming from poverty, desperation, or disenfranchisement. Sure, you need an ideology, but that ideology will not gain widespread traction if circumstances don't favor it. Such circumstances did not exist in Iraq until 2003 (except for the Kurds). They exist now, which is why IS happened now and not in 2002. Religion absolutely fills this hole, but it is by no means the only thing that does. Communism did the job perfectly well in both Russia and China. If circumstances in a region favor the development of terrorist or rebel movements, a suitable ideology will be found. It happens
every time.
And I think Islam is as compatible with western liberalism as Christianity is. It is no less mutable.