Stanford, Calif.

The woman sitting opposite me, dressed in a charcoal pantsuit and a duck-egg-blue turtleneck, can’t go anywhere, at any time of day, without a bodyguard. She is soft-spoken and irrepressibly sane, but also—in the eyes of those who would rather cut her throat than listen to what she says—the most dangerous foe of Islamist extremism in the Western world. We are in a secure room at a sprawling university, but the queasiness in my chest takes a while to go away. I’m talking to a woman with multiple fatwas on...