What is the current state of the law on freedom of speech in the context of defamation claims?

While the right of free speech provides absolute protection to statements which are purely opinions, Gertz v. Welch, 418 U.S. at 339-40, 94 S.Ct. at 3006-07, it is conceded that statements clothed as opinion which imply that they are based on undisclosed, defamatory facts are not protected. This stricture on publication of opinion rests on the assumption that, given all the facts of a situation, the public can independently evaluate the merits of even the most outrageous opinion and discredit those that are unfounded. On the other hand, when an opinion held out for belief is stated so that the average listener would infer that the speaker had an undisclosed factual basis for holding the opinion, the listener does not have the tools necessary to independently evaluate the opinion and may rely on unfounded opinion that defames an individual.