As the reported evidence of incitement to racial hatred was about as stark as it is possible to imagine, the only reason the CPS could plausibly have held fire is a belief that the "public interest" would not be best served by a trial. Supplying the oxygen of publicity to a viciously racist group was, seemingly, judged inappropriate.
Yet the current Code for Crown Prosecutors lists among "public interest factors in favour of prosecutions": 1) where the offence is committed by a group, and 2) where the offence was motivated by racism. Laws cannot banish racism, but the ugly issue must be dissected in open public debate, not coyly kept out of the courts and the media.
Dr Gary Slapper