I agree. But when I condemn this sort of quackery, people sometimes ask me why I have to be such a downer... what's wrong with placebo? If it's helping someone, then why not just let it be?
In the words of Prof. Ernst,
The answer is that it prevents clinicians telling the truth to patients. Being honest would defeat any placebo effect: if I tell my patient, "Take this remedy; it contains nothing and the trial data shows nothing," she is unlikely to experience a placebo response. Hence, homoeopaths, knowingly or unknowingly, deprive patients of informed consent. This paternalistic approach is recognised as unethical.
Furthermore, he points out that the placebo effect is often slight, unpredictable, and short-lived.
Prof. Ernst says that If you want someone to experience the placebo effect, give them a REAL treatement. Then they can benefit from both the treatment and the placebo effect (and the doctors don't have to lie).