I got into my one and only physical fight when I was in seventh grade. It was right after school let out, the other boy was called Nathan, and moments before I launched at him, he knocked the books out of my brother Casey’s hands and called him “retarded”. More than 20 years after that scuffle, I still wonder how often Casey, a now 35-year-old autistic man, is called that word. Given the current political landscape, I’m certain he’s going to start hearing it more often. The R-word is in a new era of prominence in rightwing, chronically online circles...