They live among us, perfectly decent people in almost every respect. You’ve probably known them for years. They give to charity and pay their taxes. Some even return their library books before they’re due out of consideration to others who want to read them. They just won’t acknowledge your greeting when you pass them in the hall.
The refusal to acknowledge greetings should not be confused with those suffering from “resting brat face,” that dreaded malady that makes it appear that those who suffer from it just sucked on a lemon. No, RBF is an involuntary condition, while those who ignore a genial “Good morning!” are making a conscious decision to do so. I can only assume they’re missing a gene or were unable to watch key episodes of Mr. Rogers’ Neighborhood as children.