It doesn’t really matter whether Mr. Trump is truly a racist or merely playing one on television to appeal to his base. Either way, his path can lead to bloodshed. We’ve seen this movie before in the radicalization of Muslims by internet sermons delivered by charismatic, father-figure clerics who inspire terrorism and martyrdom.

Before El Paso, I said that when the next act of racial violence occurred, we would hear White House officials and the Republican leadership claim their hands were clean because malicious people can’t be stopped from acting out. And indeed, almost immediately after the El Paso bloodshed, Republican leaders, including the president, began citing factors like mental health and video games to explain the killings.

Don’t believe a word of it. Terrorists aren’t born that way: They are inspired, cultivated and directed. Our experience with online radicalization has shown that there is a clear path to violence. Unless the path is blocked by those who built it, the journey will become even more deadly.