No Dungeons & Dragons for prisoners?

You can read the story here: http://www.nytimes.com/2010/01/27/us/27dungeons.html

From the article:
Dungeons & Dragons could “foster an inmate’s obsession with escaping from the real-life correctional environment, fostering hostility, violence and escape behavior,” prison officials said in court.

In my own experience, people who play pencil & paper roleplaying games are less likely to want to go outside. :)

Is this too much or does it make sense to make restrictions like this for prisoners?