The choking death of a man at the hands of another New York subway rider was setting off powerful reactions Thursday, with some calling it a criminal act and others justifying the killing as defense against dangerous disorder. Manhattan prosecutors promised a “rigorous” investigation into whether to bring charges in the death of the Black man who was tackled by fellow passengers and put in a fatal chokehold by a white man, who has been described as a Marine veteran. The medical examiner’s office ruled Wednesday night that Jordan Neely, 30, died in a homicide from compression of the neck but the office said that any determination about criminal culpability would be left to the legal system.