An accusation of pedophilia is unprotected because accusations of crime are considered, at law, to be intrinsically damaging. Racism (and, to some extent, racial profiling) is not against the law: I believe it's perfectly legal to stop only black shoppers for shoplifting, for instance (so long as they're actually shoplifting), even though 60+% of shoplifters in Oberlin appear not to be black.

Here, I wonder whether it's not the speech that got the university in trouble so much as the concerted and diligent effort to harm Gibson's business through multiple means.