"Every doctor" would be wrong. The guy from the Fat Head documentary showed that you can lose weight and become healthier on an all-McDonalds diet.

Also, the food pyramid (which, admittedly, is so incorrect that it should cause you to question any healthcare professional who quotes it) does include a small layer for fat, oil, sugar, and sweets, implying you can have them as an occasional treat but not all the time. No doctor is going to tell you to never eat at McDonalds, only to make it a rare treat.