While I believe that their logic was flawed, I don't have a great problem with them removing the books - what I would have a problem with is restricting their right to have an imagination. That is what it implies in the statement - that they might fantasize about escape. No shit. Really? Fucking genius. I have never met a prisoner who didn't fancy a bit more freedom.
I don't believe they could demonstrate that D&D is a tool to enable escape. If anything, it may allow them to serve their time more peacefully and creatively instead of plotting to escape. I don't need to kill people in real life because I can get that little fantasy out of the way through my imagination... imagine what would happen if the only way you were permitted to experience something was through the actual act of doing it?
Humans are, I believe, the only species that has been proven to have the ability to learn from hypothetical scenarios. We don't have to learn solely from our own or others' mistakes - we can visualize an outcome based solely on other experiences and extrapolate a plausible outcome and by doing so, choose to act in a manner that would either likely bring about or avoid that outcome.
Would they take away his pencil and paper if he started writing fiction about a prisoner? How about if it wasn't fiction but was a journal? Many psychologists recommend people to document their experiences and thoughts and reflect on them. When does that cross this line that they are imposing?
Anyway, just saying. My sympathy is mitigated by his crime, but just because he killed someone doesn't mean he stopped being human. That is a genetic discussion and not open to behavioural debate - his actions may reflect more appropriately on another species, but he still is one of our species. Whether we like it or not.
That also opens the door to what level of punishment is appropriate for which crime - does all incarceration carry the same rules? What if he was guilty of tax fraud and was in jail? Would it then be ok for him to game?