What should I do if a person is angry and goes on a hunger strike, doesn’t speak, and coaxing is of no use?

It’s very simple to use a hunger strike to blackmail others. Ignore them. Eat, drink, and play when it’s time. Ignore them and see who can’t stand it first. What’s wrong with the hunger strike? I've seen someone hit himself in the mouth, so I just watched and sat down to watch him hit himself. As soon as he heard it, I told him to keep going. If he doesn't feel pain and I don't feel pain, I can just hit him. There are a few times. Well, after all, it is himself who is harmed