I was scheduled to speak last week at Dartmouth College by invitation of the chapter College Republicans and Turning Point USA. The Thursday “Extremism in America” event was meant to highlight America’s long history with far-left violent extremism, a subject politicians and media oft ignore and deny. Gabriel Nadales, a former member of California militant leftist groups, was the co-speaker. But we never got to step on stage to a live audience. Soon after the event was announced, Antifa and its army of online trolls threatened violence to shut it down. In turn, Dartmouth administrators gave the extremists exactly what...