These is an old adage that if you want to trash somebody in a novel without getting sued for libel, all you have to do is write that the character has a very tiny penis.
Nobody is going to sue you for libel and come forward saying:
“Yes, that’s me in the book, the guy with the teeny weenie”.
There is even a name for this tactic, it's called the “small penis rule”!
This is funny case by Michael Crichton . The link describes how Crichton trashed a phoney scientist who endorsed the Global Warming hoax by describing him as an anal sex pedophile:
"The defendant, thirty-year-old Mick Crowley, was a Washington-based political columnist who was visiting his sister-in-law when he experienced an overwhelming urge to have anal sex with her young son, still in diapers."
Enzyte: Exception to the tiny penis rule
However, there are exceptions to the tiny penis rule.
When a shyster Steve Warshak started selling a phony penis enlargement product called “Enzyte” he relied on the tiny penis rule to protect him, thinking that no man was ever doing to ask for a refund because their member remained microscopic.
This article shows the peril of relying on the tiny penis rule.
Steve Warshak got 25 year in jail after over-billing for Enzyte, but the TV commercials were hilarious, a masterpiece of marketing genius!