They are not: a difference of opinion. a difference of interpretation of facts. For example, I am a Republican in more or less the mold of Theodore Roosevelt. My father (who grew up on a farm during the Depression) is a New Deal Democrat. We have differences of opinion and interpretations of facts. Neither one of us thinks the other is a liar. Slander (from the American Heritage Dictionary): Oral communication of false statements injurious to a person's reputation. A false and malicious statement or report about a person. Further, Slander is verbal\oral. Libel involves defamation in other forms of communication, for example: the written word, images, or here on the Board. So, Slander is not: Asking for proof of a statement. Asking how an opinion was arrived at. Responding to a comment based on a poster's previous posts on the same or other relevant threads. Please consider this from Wikipedia: http://en.wikipedia.org/wiki/Defamation In my experience, truth like chlorine bleach is the best for dealing with the stain of libel or slander.