In April, a long-haired flower child on the campus of Princeton University was captured on camera. The picture, posted on social media, shows him sitting on his guitar case, guitar in hand, ready to play. Spread on the grass before him, completing this otherwise faithful portrait of hippiedom, is not a peace sign or a tie-dyed bedsheet but the flag of the terrorist organization Hezbollah. Look closer, and you’ll spot the keffiyeh around his neck. But what is incongruous about the picture—the pairing of hippie garb and jihadist imagery—is nothing of the sort in real life. This tree-hugging terrorist supporter is the moronic face of a harmonious marriage.

In the first decade of the 21st century, the United States was attacked by…