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Now let’s dig around the mammalian systems and watch him twitch. It turns out that most humans crave the security of their tribe. It was sociologist Henri Tajfel who formally identified the tendency to categorize in-groups versus out-groups. He theorized that we use out-group derogation to bolster the collective self-esteem of our own crew. The resulting camaraderie bonds us to our team, and prejudice guards against the risk of outside threats. A recent psychological experiment highlights another mechanism at work: guilt projection. Whenever a person is blamed for a wrongdoing, they tend to launch accusations at some hapless fall guy. Yeah, these are tired ploys, but damned if they don”€™t keep the barbarians on their side of the gate.

Cut a little deeper and we uncover the disgust reflex. People are hardwired to get triggered whenever they come into contact with potential contaminants: feces, disfigured faces, alien sexual fluids, decomposing organic matter, dead bodies. Any object that may be contagious, we instinctively avoid. And anything that comes into contact with a disgusting object is immediately seen as contaminated to the core. Most important, our minds are programmed to perceive contamination as running in one direction. To take a classic example: Imagine someone touching an apple with a turd. You don”€™t suddenly want to eat the turd. You want to throw the apple away. As we progressed from the savanna to the village, this response has come to include morally degrading behaviors and any person suspected of indulging them.

Each of these neural gears turns with the others. Vigilant danger detection, out-group demonization, disgusting associations”€”it takes arduous training to get a few steps ahead of knee-jerk responses. It then requires constant self-discipline to keep them under control, and no effort at all to let them take over. One minute we”€™re having a civilized discussion, the next we”€™re smashing each other like a pack of screeching macaques punching at sticks in the grass.

Our dissected subject, now reduced to a drooling mess on the operating table, appears to have fallen victim to his own instincts. He stares out the window and swears he sees Nazis in the clouds.

Final diagnosis: This asshole must be a Marxist.