"Once we vaporize mecca it would prove their entire religion is a sham"
I don't think they're logical enough to realize after Mecca's destruction that their religion is a sham. They've well established their irrationality. My gut feeling is that they'd keep on keepin' on with the beheadings, misogyny, wild-eyed intolerance, chest-thumping, blood-letting, effigy burning, suicide bombing, baby killing, and so on...ad bloody nauseam...