LONDON – The fatal stabbing of a British teenager who was handcuffed by police while his killer stood nearby erupted into a debate Tuesday about policing, race and knife crime.The killing of Henry Nowak, 18, happened in December, but the story got renewed attention after the killer was sentenced to life with a minimum of 21 years in prison Monday, and video was released that showed police not believing Nowak when he said that he had been stabbed.Recommended VideosThe killer, Vickrum Digwa, 23, who is Sikh, had reported to police that he was the victim of a racist attack by...