We have all seen the appalling and, apparently ever growing, incidents of teenage knife crime reported in the media. Certain elements of the press seem to take a perverse joy in screaming headlines at their readers, predicting the collapse of society and laying the blame at whichever door is open at the time. Immigration. Lack of family values. Too aggressive policing. Policing that is too liberal and afraid of being accused of racism. Schools. Lack of funding. Quamari Barnes –…