Jack Thompson has been repeatedly bashing Rockstar's upcoming The Warriors, complaining that it's a violent game based on a violent movie. That much is probably true. However, he also goes on to state:
That is false.
Paramount did indeed stop advertising the film on February 16th, 1979 ... but it was in reaction to sporadic outbreaks of violence at the theatres it was being shown at, not because of any new copycat crimes or increase in gang violence overall.
One week later, they restarted their advertising campaign and allowed exhibitors to be released from their contracts if they felt showing the film might cause any safety issues.
Apparently few did, since the film went on to gross $12 million in two weeks.
Source: 1979 Oscar Chronicle