Wikipedia describes a red herring fallacy as follows:
A red herring is something that misleads or distracts from a relevant
or important issue.
The OP quotes from a book called The Art of Deception. It appears the book is an attempt to show the reader how to use a deceptive argument hopefully with the goal of making the reader realize what is going on when the reader hears such arguments from real deceivers.
Consider this from the quote:
But what happens if you feel that your defense has not be[en] strong
enough or that there are lingering doubts in the minds of the
audience? At this point you should avoid sticking to the point.
Remember that the only thing that always sticks to the point is a dead
insect on display. What you must do is draw attention to a side issue
where you feel particularly strong.
The reason to engage in the deception is because one's defense has not been strong enough. What should a deceiver do? The author, playing the role of the deceiver, suggests that the reader, who supposedly also wants to become a deceiver, stop sticking to the point. Distract the listeners by throwing them a red herring to play with so they do not focus on the real issue. Draw their attention to a side issue where the deceiver can make a stronger argument.
With that as preliminary, here is the question: I agree that dead insects on display stick to a specific location (on a window pane), but how's this (the emboldened sentence) relevant to the Fallacy of Red Herring?
The author playing the role of a deceiver is trying to instruct the reader into becoming a deceiver by suggesting that the reader use a red herring argument when it is to the reader's advantage. Why not? If one does not use a red herring argument then one is sticking to the point but that is a weak point for the deceiver. The author humorously notes that only dead insects on a pin stick to the point.