Read the passage. My humor column in the school paper was supposed to make people laugh at the cafeteria's mystery casserole. I included a joke about a student who always brought food from home, and by lunch she was eating alone. I wanted to say people were too sensitive, but I had used her as a shortcut to an easy laugh. In the next issue, I apologized and rewrote the column about the menu without naming anyone. The joke I lost taught me more about writing than the one I had printed. What is the passage's central focus?