I don't know if it's an existential risk, but if technology keeps enabling fewer and fewer people to kill more and more people for less and less money (hint: it will), and Islamic countries continue to produce as many people who want to kill us as they do now, then at some point, perhaps 50 years from now, "we" will have to kill everyone in every country where radical Islam has a hold. (That's about 400 million people at present.)

Hey guys, defection has gotten really easy... screw cooperation, let's start defecting all over the place!