Given that ethics are derived from a person/peoples morals. You have to look at it in two ways:
1. From the point of view of a scientist (or any person holding hard facts on the subject at hand), yes it is unethical as they are spreading misinformation which could have serious implications. Take a patient with cancer which has a 80% mortality rate, providing the patient undergoes a specific (and possibly uncomfortable) set of treatments without which the 20% chance of survival is not possible (effectively making it terminal). To a doctor, a homeopathy advisor telling that patient with cancer (s)he has an alternative cure/therapy, that is unethical. Obviously it is up to the patient to decide on using said treatment, but at best it is giving false hope to a patient and could lead them into giving up the proven treatment in favour of some promised 'miracle cure' which apparently has no side effects or pain associated with it and will cure him/her, despite there being no scientific data to substantiate any of the claims made. It could be viewed that the homeopathy advisor is being ignorant to scientific fact on the products (s)he is selling, and also ignorance to scientific fact on the part of the patient. Given the stress and uncertainty the patient is undergoing during their regular hospital treatment, it would be unethical for such a person to approach them at such a vulnerable time and effectively convince them they have the answer to all their problems, even if under the cover of 'giving advice'.
2. However, from the point of view of the homeopathy advisor, it certainly isn't unethical. To them the doctors are being ignorant to their ways (despite scientific fact). They would view what they do as advising patients of alternative therapies that are available and as such in the patients best interest. They would consider a doctor unethical to advise against the alternative therapies.
It all comes down to a point of view. I personally have a strong dislike for homeopathy as it bring false hope to people in extremely vulnerable positions, and relies on a populations misunderstandings in order to sell its products. From the evidence presented to me, I have come to a reasonable conclusion that homeopathy medicines have little more than the placebo effect. I find it unethical to sell a product which quite literally does nothing but fool you.
I think under this circumstance, you must allow people to make their own decisions based on hard facts. It most certainly is unethical to give a person a load of BS and convince them that it is fact, thereby skewing their view of a subject and causing them to become ignorant of said subject. By presenting the hard evidence to them, in this case that these products do not work, they must make their own decision on the matter. If they choose to ignore the facts in front of them, that's their choice, but as far as I'm concerned for a person to view the facts on a subject such as this and disregard them (I accept a terminal patient or seriously ill person is going to be in a vulnerable position and willing to try anything), is pure ignorance.
Ignore: "to refrain from noticing or recognizing".
Ignorance: "lack of knowledge, education, or awareness ".
Ignorant: "lacking in knowledge or training; unlearned".
Those are the definitions, and they apply here and in many other places. A lot of people believe only what is said in the media (particularly the hype and misinformation) simply because they have a lack of understanding of the subject matter.
Is it unethical to mislead someone whether a seriously ill person or an entire public, I would say yes. It is the misinformation given by these people (media, homeopathy advisors etc.), whether initially or over a period of time that causes people to want to ignore the actual facts of a matter and only accept what supports their cause.