"We object to any media which represents sex workers as legitimate targets of violence, rape and murder," the organization stated, noting that it vigorously opposes censorship.
SWOP said it issued the statement to alert other parents to the potential danger of some of the game's themes.
"Grand Theft Auto accrues points to players for the depiction of the rape and murder of prostitutes (and is a product) which encourage(s) the denigration and destruction of prostitutes," SWOP said.
Though porn stars like Jenna Jameson have lent their voices to GTA (it has several editions, such as the original game, Vice City, San Andreas, and Liberty City), SWOP says the game's hookers are singled out for violence.
People who have played the game dispute the rape and point-accrual charge, saying that GTA's violence is universal and pro-bono.
Nor are prostitutes raped in GTA, but they are indeed the victims of economic and physical violence.
"Getting blowjobs from hookers in the game costs you money, but provides a health boost," said Stephen Johnson (no relation to Grip), web producer of G4 Videogame Television's Attack of the Show. "After the health boost is gained, it's possible to kill the hooker and get your money back, much like real life."
A spokesperson for New York's Take-Two Interactive, which owns Rockstar Games, did not return calls in time for publication.