Imagine transcription: An image of Light Yagami, Misa Amane, and L from Death Note on a fiery background. The caption reads: "Did you know, in the anime 'Death Note' for copyright reasons, the milk has to be spelt 'MLK' on the cartons? Google 'MLK Death Note' to find out more!". End transcription.
They didn't have to be true. The implication was that they could make the public believe such things were true, which at the time would have ended him.
Obviously in a reasonable world no one should give the slightest fuck about someone else's orgies, but unfortunately a lot of people have puritan brainrot, which was much, much more widespread at the time.
But they were writing the letter under the guise of just being some guy. I'd believe the government could make the public think I'm some sexual deviant, but not a random person writing a letter to me.
Oh that's a good point