What is the meaning of [When in doubt leave out]

This advice applies particularly to writers who are either not sure of their
facts, or cannot make up their minds whether or not to include a passage that
pleases them but may not please all their readers.

> ‘Dear Arthur – Many thanks for letting me read the manuscript of your
reminiscences. I find them lively and interesting reading, but venture to
suggest leaving out the anecdote about the Noble Lord, the Admiral’s daughter
and the cauliflowers. It’s certainly very funny, but you don’t want a libel
action on your hands.’