How can reader's distinguish between prejudicial and non-prejudicial use of rhetorical devices?
How can a person distinguish between the prejudical and nonprejudical use of rhetorical devices?
A prejudicial use of rhetoric will often have little backing, or use faulty evidence such as gross generalizations, circular logic, and stereotyping.
By nature, a prejudiced usage will show as having been made based on previous thoughts, evidences, etc. without looking at the facts currently at hand. So look for things that prove this point.