I wasn't arguing the validity of the publicity argument other then why would they really bother? Truly, if it came to it, they'd be in the right legally speaking. But, what money would they get from anyone is the other thing. Would be a might hard to collect damages.
Ah, but not every legal dispute ever makes it to court. Usually, the copyright owner begins by simply sending a letter, or, in some cases, an email message, to the webmaster asking them to cease and desist. In the case of fan web sites, usually the fear of ticking off the actor, director, etc., is enough to make them stop.
If they stupidly continue, there are other avenues to pursue long before it shows up in court. The copyright owner need only notify the entity that hosts the web site under guidelines laid out in the Digital Millennium Copyright Act of 1998 (aka the DMCA), and the entire site will usually be yanked for violating the host's Terms of Service.
As part of the web consulting work I do, I've been involved with situations where an email was sent to a webmaster about a copyright issue, and I've also been involved in a situation where a web host was contacted under the DMCA guidelines. Both are cheap, quick and relatively painless processes for the copyright owners.