In layman’s terms, a statement cannot constitute libel or slander unless it is provably false and the defendant either knew it was false or reasonably could have known.
The statement must be shown to have caused actual injury.
The statement must be shown to have been made with malicious intent.

This is a pretty tall order. The bar has traditionally been set so high in this country to keep defamation claims from serving to undermine and subvert the First Amendment right of free expression.