The modern movie ratings system was put in place by the Motion Picture Association of America in 1968 for parents to protect children under 18 from ultraviolent or sexually explicit material. Since 1968, avant-garde leftists have been trying to knock this voluntary system down.
The most recent example came with the raging ten-minute lesbian-sex scene that wowed the Cannes Film Festival (and won their Golden Palm) in "Blue Is the Warmest Color." The IFC Center in New York's Greenwich Village decided to shred the NC-17 rating for this movie because "it is our judgment that it is appropriate for mature, inquiring teenagers who are looking ahead to the emotional challenges and opportunities that adulthood holds."