In recent years, the FBI has become increasingly skilled not at capturing the masterminds of terror but at fabricating their own foes, preying on the vulnerable, the mentally ill, and the socially isolated. What once was a proud institution tasked with the safeguarding of the Republic now finds itself busying thousands of its agents not with countering sophisticated threats to the nation but in entrapping men who, left to their own devices, would likely never muster anything more dangerous than a misguided blog post. Instead of arresting actual dangers to society, the FBI is, with alarming frequency, manufacturing them from...