Mazes and Monsters
Mazes and Monsters is a (far out game) really cheesy book (1981) and movie (1982) that portrayed the titular game Mazes and Monsters, an obvious reference to Dungeons & Dragons, as a dangerous pasttime, suggesting that people got too wrapped up in the game and became suicidal or otherwise went completely batshit bonkers. The movie is only notable for its connection to traditional gaming, its propensity for being stupidly inaccurate, its LOLHEUG figures, and being the first movie Tom Hanks was in AFAIK. It's pretty shit. The movie also features some moron who kept wearing inappropriate hats all of the time, like wearing a suit and a construction helmet to a party, LOL SO RANDOM.
The story features Tom Hanks' character, Robbie, being seduced into the world of Mazes and Monsters by the feminine wiles of a female gamer (remember that inaccuracy we mentioned?). Jay, the aforementioned hat man, becomes suicidal for some reason and heads off to find a quiet place to off himself. Unfortunately, before he can manage to do so, he instead decides to do something even worse: LARP. Convincing his friends from the table to join him in the great outdoors by shitting all over the existing campaign, he declares himself "Maze Controller" and has them explore some caverns, at which point Robbie immediately dives straight into the deep end of Lake Nutjob and starts hallucinating monsters everywhere, assuming the personality of his cleric Pardue.
Now believing himself far too holy to have sex with his girlfriend (who suggests that this seems to happen to her a lot), he has a bizarre dream and winds up in New York seeking the Twin Towers. He proceeds to stab a mugger in self defense (we are for some reason supposed to take this as horrific even though we'd probably do the same thing) and temporarily resurfaces from beneath the crazy waters just long enough to call his friends and tell them where he is, at which point they realize his predicament and go to recover him. Sadly, so great is the hold of Mazes and Monsters on poor Robbie's mind that even once he has been rescued from the terrible fate of trying to fly off the top of the World Trade Centre (seriously, Fly isn't even on the cleric spell list. What a noob) he still believes he is Pardue the Holy Man. The story ends with Pardue kept under close watch by his family as his friends hope that he will one day recover, while simultaneously furthering his delusions with a nostalgic last game of M&M.
This movie's message is pure FAIL when you notice that the rest of the players left the game without any problems, and Robbie is clearly insane and what he went through wouldn't happen to a normal person, or most weirdos, for that matter.
Mandatory Boring History Lesson
The movie is, as stated above, based on a book, which itself is loosely based (seriously by loosely I mean it's about as historically accurate as Abe Lincoln: Vampire Hunter) on the story of James Dallas Egbert III, a college student. He snuck into a steam tunnel to commit suicide, but was rescued. A private investigator, William Dear, looked into it, and reported his findings (which weren't D&D related, but it was mentioned that he played D&D). The news picked it up and as far as they were concerned it was just one more bad thing to say "BLAME D&D!!111!!!" He later killed himself with a gun, and again the media was eager to blame D&D, and some idiot writer wrote Mazes and Monsters. The reality is that D&D had nothing to do with it. He was a 17 year old college student with clinical depression, parental issues, drug addiction, and was hypothesized to be a closeted gay man who felt alone by Dear, who just couldn't take this shit anymore and offed himself. Then the woman who wrote Mazes and Monsters, Rona Jaffe (a second-wave feminist who seemed relatively reasonable other than the book) didn't know jack shit about it and wrote a book based on a position she already held. As did Jack Chick, the nice fellow who wrote Dark Dungeons.
tl;dr: A bunch of idiots who don't know what they're talking about wrote a book about how D&D is bad, and then made it into a movie, which helped kick off the Satanic Panic, against the advisement of literally every professional involved..