They shoot horses, don't they? How valid are the arguments of opponents against euthanasia?

In this article the arguments against euthanasia are examined. One of the weightiest arguments of mental health professionals against the practice of euthanasia is that a doctor's active commitment to euthanasia can be interpreted as causing harm. It is investigated whether this statement can be ethically justified on the basis of the text of the medical oath or medical declaration. Furthermore, it will be discussed whether it is ethically acceptable when doctors refuse a) to help candidates of euthanasia who (would likely) meet the legal standards of euthanasia, or b) to refer them to a colleague.