I actually don't agree with that. While I am willing to believe that the average doctor's understanding of nutrition is incomplete, I doubt the average punter's is any better.
Most people I personally know that "self-medicate" with advice they found on the Internet or read from some popular pseudo-science book seem to be engaging in magical thinking, and/or doing a great job ruining their own health by themselves. Perhaps you run with a more informed crowd.
I do agree that taking responsibility for your own health is a difficult, time consuming task that may be highly wasted if one can't distinguish between valid and invalid information. I wish I could figure out a way to help people with this process. If I show someone scientifically dense information their eyes glaze over.