The primary purpose of the criminal justice system is to keep society safe, not to rehabilitate criminals. If doing the latter assists that purpose, then fine. "Punishment" only makes sense in the context of educating the convict that what he did was wrong; don't do it again. Nothing about this story suggests this guy is a psychopath whose potential value to society will never exceed the risk of having him loose among us. While the manner of his crime may have been gruesome, there's not enough detail here on why he did it, and I suspect a life sentence is inappropriate. If he had a history of [violent] criminal behavior, he probably should have been put down, but if this was a hot-blooded response to the bf giving his sister a black eye, it doesn't take years in jail to teach him not to take such matters into his own hands (a year or two ought to do, maybe followed by another year or two of probation). Still, while serving his sentence, about the only right he has is to a minimal standard of care. He has no right to play D&D.
That said, if there is ongoing gang activity in the jail that is not consistent with the goal of keeping society safe, then the most cost effective means of dealing with it is most likely identifying the involved inmates and putting them down. Game over.