schizophrenics often reject medication in the midst of psychosis, while agreeing it's necessary when they're lucid.
lots of addicts genuinely want to kick the habit, but their willpower fails them. drugs like disulfiram and naltrexone can help by making highs unpleasant or unattainable.
sex offenders who abuse minors are sometimes chemically castrated with GnRH agonists as part of their parole. this reduces their sex drive by depriving them of androgens, reducing the risk they'll reoffend.
where to draw the line is complicated, but at least in the schizophrenic case I really think forced medication compliance helps everyone. if you're not lucid you aren't competent to make medical decisions.
