“They were looking for trouble harassing everyone they saw,” said the victim, who did not want be identified. “When they started to bother the cab driver, I went over and told them to leave him alone. That’s when one coward hit me from behind with a backpack.”

A man was stabbed and left fighting for his life after scuffling with a stranger who had stepped on his shoes during their rush hour commute in Manhattan Friday morning, cops and sources said.