It was in no way the correct decision, because a few social workers and a lone voice police woman knew exactly what was happening and had the evidence to prove it.
Every time it was "sent upstairs", the powers that be buried it because it was seen as a political hot potato. They even blamed the under age girls, due to their promiscuity ! 
It was a combination of not wanting to get on the wrong side of people who carried a lot of power and influence in the localities (which is why the perpetrators thought they could act with impunity) and collective cowardice / dereliction of duty, by people whose job it is to be brave and take their duties very seriously.
Ah, you misunderstand me, the decision not to investigate was clearly wrong for the reasons you cited, however the OP was specifically talking about the testimony/support of the point by Nick Griffin. That, is the part which I feel should rightly be ignored. It's only with hindsight that you can pick out this truth from all the other drivel the BNP and other such disreputable organisations put out on a daily basis.
The deliberate suppression of evidence on the grounds of not upsetting people/political correctness which you describe is categorically wrong and in my view those involved should be sacked, and pursued to the fullest extent of both civil and criminal law. In many areas we have totally lost our objectivity as a nation, along with most of our common sense it seems.
Not objectivity, Identity

For the last 40 years or so, we have been brainwashed into believing whatever our lords and masters at Number 10 say.
If you dare to disagree, you are branded a racist, a homophobe or a sexist.
Tony B Liar ( and he wasn't the first ) openly invited any 3rd world oppser and there ideas that would come here on the pretence that those who come here will vote for him for ever and ever so keeping the idiot in power for as long as he wanted to stay.
If we objected in anyway, we was hounded be the lefftie brigade and told to repent our sins or be dammed to have hot forks stuck up our arses for eternity.
Nowadays, we are just a multicultural / no specific gender shithole were whoever shouts the loudest or whoever has the brightest flag wins.
But hey, as long as our masters are happy who gives a fooook ............