This is a very good question. The answer is simple. We aren't barbarians. We have evolved since the 7th century. Here's a good question for you: If we sent a bunch of ICBMs into Mecca on 9/10/01 for no other reason but to slaughter innocents, what would muslims do to every living non-muslim in every country on earth?
Considering the inferior cultures they've produced with their intolerance, I doubt they'd have the power to do much to the rest of the world.
They might murder a few thousand helpless civilians, but they aren't in a position to start a real war.