It’s legal for me to expose your infidelity.
And it’s legal for me to seek $10,000 from you in a business transaction.
So why is it illegal for me to blackmail you for $10,000?
“Most crimes do not need theories to explain why the behavior is criminal,” writes Northwestern law professor James Lindgren. “The wrongdoing is self-evident. But blackmail is unique among major crimes: no one has yet figured out why it ought to be illegal.”