Disgust evolved to protect us from contamination — spoiled food, disease, waste. Research by Rozin, Haidt, and others shows it also migrated into the moral and social domain, where it attaches to people and ideas and produces an unusually fast, sticky, and hard-to-argue-with rejection. That is what makes it valuable to a manipulator: a target framed as disgusting is dismissed before any argument is heard, and the feeling resists correction by facts.
The tactic pairs a human group with the language and imagery of contamination — vermin, filth, disease, infestation — then generalizes it from a few examples to the entire category, erasing the individuals inside it. Once “they” register as polluting rather than merely disagreeing, exclusion and hostility feel not just acceptable but hygienic, which is why purity and “cleansing” language so reliably accompanies it.
This is the emotional engine of dehumanization (T9.17) and enemy-image propaganda (T23.1), and historically it has been a precursor to persecution and violence — which is why its risk sits high despite requiring no sophistication. The defense is to interrupt the blur: name the dehumanizing move when you see it, re-individualize the caricatured group, and hold people accountable only for specific, verified conduct rather than for a category framed as contaminating.