Suppose a person has a constant, uncontrollable desire to inflict pain on emself. This is distinct from masochism, because a masochist can in some sense be said to enjoy the pain. But this person feels only unpleasant experiences when ey inflicts pain on emself. Ey feels terribly unhappy in ever possible sense, but still feels a strong desire to experience more pain.

Should preference utilitarians accept that it is morally right to inflict pain on this person?

This is one of the reasons I reject preference util

There's no free will, so the parson can't decide whether to have a certain desire or not. So we cannot inflict pain on this person and meanwhile making the person resonsible for it because of it's arbitrary preferences.

But it is very easy to critisize preference utilitarianism from the standpoint of hedonic utilitarianism.

To show how absurd preference utilitarianism is we should rather imagine a person who has a strong preference for their preferences being frustrated. This could be possible if this person would deeply hate itself. I think that there are a lot of people who sometimes unconsciously behave that way. So how should we deal with these people?