Bonnell’s experience validates the vague liberal concern that infectious ideas are spreading online. But this popular notion commits itself to a perfunctory metaphor—that ideas are pathogens passed from one mind to the next upon exposure. The YouTube user is not an independent moral agent but a helpless victim of the algorithm. The liberal complaint isn’t that YouTube is engaged in a kind of social engineering; it’s that the platform is engineering for a politically undesirable output. Bonnell’s approach to radicalization, so far, could not be further from this casual anti-intellectualism.