The comments referred to "savages" and "animals." One person wrote, "Let them kill each other."
The raucous annual parade is a heavily policed event. It's one of the city's largest outdoors events and has been marred by violence in some years.
Three shootings were tied to the parade in 2011, and police seized 14 guns during the celebration the night before the parade.
Police spokesman Paul Browne tells The New York Times that among the 17 employees were four police officers who still face departmental trials on charges of "conduct prejudicial to the good order of the police department."