4. “DENIER” This slur is used to shame or silence global-warming skeptics and other heretics who question conventional wisdom. It has an ugly provenance, too, coming from “Holocaust denier,” a description applied to those best described as neo-Nazis or lunatics (or both). But skepticism is not a sin. The famed Chicago City News Bureau popularized a journalistic bromide: “If you mother says she loves you, check it out.” It means get a second source, be careful, and don’t just repeat what you hear. Words to live by. (By the way, my Twain reference comes from “Life on the Mississippi,” Chapter 6.)