Did you even read the article? It's concerned with drink-related violence (not gang violence), and states fairly clearly that generally the reason that these ty

Did you even read the article? It's concerned with drink-related violence (not gang violence), and states fairly clearly that generally the reason that these types of crimes are not reported is because they happen in clubs/bars and the perpetrator is often not known. They clearly state that data is anonymised, and there's absolutely no suggestion that the reports are ever used for criminal investigations. The main issue that this programme tackles (apparently quite effectively) is that the police often aren't even aware that an assault has taken place (and so can't target the area it happened in). Certainly in some gang-related crimes the victims refuse to talk to anyone, but this is a very different situation. How is reducing violent crime by somewhere between 30 and 40% a bad idea?