Which of course in some closed mind paradigms is in fact true for those believe in it. There are some very large players in using MLM as one of the late 20th Century means of produc and service distrubtion. The world has changed, and the way in which we acquire, and consume product has changed also. So lets look before open mouth and insert foot. Backman, There is one important fact missing from your well stated argument.
Business is business.
As you stated, there are honest and less honorable types in all walks of life. We may have different views on the validity and usefulness of the product. If one elects to give up the call for service as a Doctor, I see no conflict. However, there is an ethical conflict if the Dr. is doing both. Most ethicists, whose books I have read would argue, that a doctor should not engage the patient in such dual roles.