He says he put his life on the line to stop a killer — and claims cops sat back and watched. But city lawyers are arguing that the police had no legal duty to protect Joseph Lozito, the Long Island dad stabbed seven times trying to subdue madman Maksim Gelman — a courtroom maneuver the subway hero calls “disgraceful.” A judge is currently deciding whether Lozito, who sued the city last year for failing to prevent the attack, will get his day in court.