You have someone who has demonstrated a mental illness that not only made them attack an innocent man, but mutilate and (if I understand correctly) start to eat him. And you say execution of this individual is "barbaric"?
This is not someone who's a lil' depressed here: this is a clear and present danger to society at large. How long before he's released as "cured"? What happens when he misses his meds? Who has to deal with the mess then?
I'm not advocating execution of everyone with a slight imbalance to their bodily chemistry. I AM suggesting that removing such a threat from society is the best way to proceed.
Housing them in a "secure mental facility" will only work as long as he's kept there. And there have been many (FAR too many) who get released, only to cause more trouble down the road. Because we don't want to be labeled "barbaric".
Case in MA. Sexual predator, been in the system as an offender since he was a young teen. Released (IIRC, against doctor's reccomendations), dodged supervision (which is NOT hard), and ended up molesting a young boy IN THE PUBLIC LIBRARY.
Because we're not "barbaric".
Recall an interview with a prison psychologist, who had (at the time) been with the system for 30 years. When asked how many sexual offenders had been "rehabilitated", he answered "none".
These people are considered "mentally unstable". They're a threat to society. But we won't execute them, for fear of the label "barbarian". Because we're "more advanced than that".
People, having dealt (directly) with people who are mentally unstable, I'm gonna go out on a limb here and accept the label "barbarian". If prefering to remove such a clear and present danger from society makes me "barbaric", fine.
But I'll bet that you'll sleep better at night, knowing that "barbarians" like me are willing to take that hit, so that "more civilized" folks like yourselves don't have to worry about getting et (or having your children raped, or sold into slavery, or...)