Stories that use these words are much more likely than others to be involved in libel suits. Calling someone a "coward" or a "fool" in print is a quick way to learn more about the judicial system than you really want to know. Here's a list of "danger words" compiled by Bruce Sanford, counsel for the Society of Professional Journalists.
Groveling office seeker
Sold his influence
Stuffed the ballot box
Unworthy of credit
Does this mean you never use the word "villian" or "thief" in a story? Of course not. This list is simply a tool to help you identify possible problem areas so you can be sure that you're saying exactly what you mean to say, and can think about whether you're ready to defend your words in court.