No job is beneath him, but he has a moral debt to pay either to society or to his parents depending upon how his PhD was financed. He has such opportunities before him if he would only think more positively and creatively.
Unfortunately he has chosen to specialise academically in a less commercial subject and needs to think laterally about the skills and knowledge that he has gained. For example things like how to structure a thesis, presenting ideas, how to undertake research and analysis. There will be many other areas and when he has got a good list he then needs to think about how businesses and academic institutions could use such skills and knowledge: this will then lead him to look at potential roles. and careers. He has to make things happen, a job will not come to find him.
Teaching comes to mind as an obvious route but he could think about marketing (very different from sales) or maybe something like speech writing or working for a political paty or as a lobbyist. It's a pity that he has developed an atitude and I certainly like the suggestion of volunteering or charity work. This always looks good on a CV and certainly this experience opens the mind to understand how privileged we are as well as gaining general work skills and learning how to work with other people. Employers are looking for people with good attitude who are able to work in teams and are adaptable.
I sense your frustration and I hope that things improve soon.