Imagine the following situation: You’re a 76-year-old man, happily married for nearly 30 years, with three children and two grandchildren. You’ve recently retired after 50 years of teaching at Harvard Law School. You have an unblemished personal record, though your legal and political views are controversial. You wake up on the day before New Year’s Eve to learn that two lawyers have filed a legal document that, in passing, asserts that 15 years ago you had sex on numerous occasions and in numerous locations with an underage female.

The...