I am pretty sure that there is a legal standard for "publishing" that is different than just "casual speech".
The major difference between kinds of defamation is libel is written, slander is spoken. The distinction isn't "written" as in printed on paper but whether it has a persistent record of it and is distributed on an ongoing basis. Almost anything on the Internet, though, is going to constitute a "publication" of some sort, and the publication is ongoing so long as the material remains available.
The issue isn't really whether it's in literal writing or spoken or on video or audio, it's the reach of it, the continuing availability of it, but most importantly, the nature of the audience and their relationship to the speaker. Chris Hansen, for purposes of defamation, is probably on the level of any TV station news broadcast or other source likely to be considered reputable by its target audience.
That's the issue. What damage is caused to the reputation by the speech. How that happens is only important in the context of what damage is caused.
In any event, not that it's a magic distinction, but what Chris Hansen is doing in this case is a lot closer to "publishing," as you're talking about it, than "casual speech." People are going to take it as an actual accusation of unlawful sexual conduct, and they're going to believe that it's actually true. It's going to damage Onision's reputation.
In short, it's defamatory per se and it's particularly defamatory because of the source.
That said, I believe it's true (which if it turns out not to be shows the importance of the speaker in this particular case). I doubt Chris Hansen is just making this shit up.
