Sources for opposition to naturopathic medicine 

American Cancer Society
http://www.cancer.org/treatment/treatmentsandsideeffects/complementaryandalternativemedicine/mindbodyandspirit/naturopathic-medicine

American Academy of Family Physicians
http://www.aafp.org/about/policies/all/naturopathic.html
http://www.aafp.org/dam/AAFP/documents/advocacy/workforce/gme/ES-FPvsNaturopaths-110810.pdf <comparing education and training between NDs and MDs specializing in family practice

NIH's National Center for Complementary and Alternative Medicine
http://nccam.nih.gov/health/naturopathy/naturopathyintro.htm#hed5

Medscape article published by Kimball C. Atwood, IV, MD
http://www.medscape.com/viewarticle/471156

Perhaps there are more??