he is putting you on the med that the drug rep told him about as he brought in lunch for his office? No? Well that is how it works, just because the Dr doesn't explain the entire process thoroughly doesn't mean he is not a good Dr or that it is unethical.
The MLM or Direct sales industry has many ethical people within it and many incredible companies that are now in the industry. Also many well know "traditional" companies started off as MLM companies, Sprint to name one.
Lumping all the companies together a "unethical" is very uneducated on your part.