According to Wikepedia:
Sophism was originally a term for the techniques taught by a highly respected group of philosophy and rhetoric teachers in ancient Greece. The derogatory modern usage of the word, suggesting an invalid argument composed of specious reasoning, is not necessarily representative of the beliefs of the original Sophists.
Rhetoric ....evolved as an important art, one that provided the orator with the forms, means, and strategies of persuading an audience of the correctness of the orator's arguments. Today the term rhetoric is generally used to refer only to the form of argumentation, often with the pejorative connotation that rhetoric is a means of obscuring the truth. Classical philosophers believed quite the contrary: the skilled use of rhetoric was essential to the discovery of truths, because it provided the means of ordering and clarifying arguments.
It does because it also appeals to the emotions and our commonplaces. But that need not mean that it does away with logic. Rather it wraps the logic (truth) up in metaphor and ornamentation etc so as to be be more persuasive.
Bad rhetoric is all about the metaphor, ornamentation etc without the logic or concern for truth. The Murdoch Press and Fox Television provide good everyday examples of this in terms fo the Iraqi war