I'll say it's NOT acceptable to be a hermit because this is what happens. Nobody is truly a hermit. In this case, this guy's contribution to the people around him was stealing their stuff. His net contribution to the world is less than zero.
The source of the problem is the hermit fallacy. Animals need other animals. Mammals need other mammals. Humans need other humans. I know of nobody who was immediately abandoned the instant they were born and who then survived fine through adulthood without any help whatsoever from any other human.
So this untermesch should be disposed of immediately then?
I don't know exactly what was going on in this chap's head but if the reported facts are correct then he would appear to be something of an exception to the rules. We don't know why he "abandoned" society or even if it was voluntary.
I do make a very specific point here: once you are outside of society, for whatever reason, it is murderiously difficult to get back in. You have no money, no bank account, no papers. You cannot account for yourself. Effectively you are a non-person. For all practical purposes you do not exist. If you try then you become subject to the full savage weight of the law. At very best you are going to be punished as a vagrant. Any unexplained murders, missing persons etc? Guess who it is going to be pinned on?
So once out, remaining outside of society may be your only real option.