Murtaza Hussain, an investigative reporter who studied the Christchurch killer’s manifesto closely, stresses that it is filled with ideas that are anything but marginal. His words, Hussain writes, are “both lucid and chillingly familiar. His references to immigrants as invaders find echoes in the language used by the president of the United States and far-right leaders across Europe. . . . For those wondering where [he] was radicalized, the answer is right out in the open. It is in our media and politics, where minorities, Muslims or otherwise, are vilified as a matter of course.”