But on the other hand, for someone who has already demonstrated that this is a serious problem, I'd be all for legally restricting them as individuals from access to anything like this. We tell convicted hackers that they're not allowed access to computers any more; we tell convicted drunk drivers that they're not allowed to drive any more; so why not tell convicted pedophiles that they're not allowed to view any materials depicting sex with children any more?
Because there's no evidence it will do any good (so far as I know). Depriving a hacker of a computer or a drunk driver of a car will, by necessity, stop them from committing the crime again. Until there's some reason to believe that depriving a child molester of porn will decrease the recidivism rate, it makes no sense to take that approach. Someone else has already pointed out the tentative evidence that access to porn may actually reduce real world sex crimes in some circumstances.