Alot of the big controversy around gaming is the result of a few people who had serious mental problems and happened to play dungeons and dragons, combine that with "magic" and "my good little christian boy playing a priest of a false god" the same people who deride Harry Potter of promoting witchcraft and evil are the ones who have been most vocal in attaching a stigma to the game.
the most notable case against d&d happened over 15 years ago, IIRC in Indiana, a young man who happened to play the game got lost in some sewers under a college campus, and comitted suicide. if you go to
A brief history of TSR , and
TSR FAQ you can get some more general info on the history of the game, if you look aorund on the site you should be able to track down the article about the suicide, and other bad press they've recieved.