How can readers distinguish between prejudicial and non-prejudicial use of rhetorical devices?

As we've said before, this question has been asked and answered a bunch of times over the past few months.

The key in understanding is in making sure you are clear on the meanings of the terminology:

prej·u·di·cial (prĕj'ə-dĭsh'əl)
adj.
Detrimental; injurious.
Causing or tending to preconceived judgment or convictions: Jurors were told not to read the newspapers to avoid being exposed to prejudicial publicity for the defendant.
(www.answers.com/prejudicial)

Non-preducial, of course, would be the opposite -- NOT using preconceived judgments or ideas.

Using the link given to you before by Ms.Sue, you should be able to draw your own conclusions. Then if you want to re-post and include what you have written up, we can critique your work for you.