Your logic suggests we shouldn't let them get their hands on anything that could be used illegally - so let's keep them away from kitchen knives, automotive repair (makes it easier to steal cars), coaching baseball (all those dangerous blunt instruments), gardening (opportunities to case houses), etc.
If precluding all future chance of nefarious activity is the goal, you don't have a system of rehabilitation, you just have an excuse to exile people.
And I would contend that if there is a lacking system of rehabilitation, you are actually causing an increase in criminal activity as well as incurring excessive expenses required to support a punishment-oriented infrastructure.
I still wouldn't agree that categorically restricting such activity is reasonable, but it's less laughable in that context.
First, in the US at least (which I know isn't the whole world, but this article is specifically about the states) the connection between being an inmate and being a bad person is weak. Many criminals are really only criminals by a technical definition - they're people who were convicted. But many of them were never actually proven beyond a reasonable doubt in a court of law - almost all of them (I mean more than 95%) took a plea deal because they had a choice between a trial and a long sentence and a plea and a short sentence). And a ridiculously huge number of them are in there for what are arguably victimless crimes (like marijuana - and we can debate that all day, but you can get a license to sell alcohol but you're a criminal for selling a drug with pretty similar impact - hardly the line between good guy / bad guy). We have about the highest incarceration rate in the world. Something is seriously wrong with our definition of criminal and how to actually reduce crime.
The second thing is that, as I said, the connection between education and a net good is very well proven. Programs that focus on being productive members of society are demonstrably far more effective than programs that just punish and disincentivize the past. Treating someone as though they can't even be trusted to learn basic coding skills because they'll probably hack into stuff is a dead end. And honestly, it's a pretty stupid one. You asked for research, and that research has been done ad-nauseum. It's just that it hasn't been listened to very well. That's probably the reason you were getting downvotes.
Just about every decision that people make constitute some kind of risk. Consider the flip side of the coin -- what is the risk of denying prisoners legitimate educational resources?
It's probably better to remove the blanket ban and apply it to individual prisoners based on their risk profile.