Well, I can't really debate the lawful aspect of it, because I'm not a UK lawyer, but I can do philosophy on it.
I think that most people would agree that incitation to violence is a crime.
Defamation (lying about someone is a way that makes them look bad) is a crime and should rightly be one to the extent that it makes a meaningful impact on a stable person's life (notably, when the portrayal makes the person look really bad and is applied on a wide scale like a publicity).
A physical assault makes such an impact and is a crime and the above simply constitutes a similar assault of a psychological nature (which can make an equally meaningful impact).
Personally, I'd also make public crucifixion of a living person's character (to the point where it's applied like a publicity and money is put into it), truthful or not, a crime if the accusations pertain to areas that are considered private (ex: what happens in the person's bedroom between 2 consenting adults where nobody gets hurt).
Generic racist remarks clearly don't apply to those areas if they don't incite to violence and are too generic to apply someone in particular, but at the same time, I would not legally penalize the resulting social stigma that follows (ex: potential employers not hiring the person based on his character).