Stress does not cause cancer (http://www.cancer.gov/cancertopics/factsheet/Risk/stress). Eating your vegetables doesn't cure cancer. Cancer is a very nasty thing, and I really run out of patience fast these days with people who promote wishful thinking as some kind of cure. Wishful thinking helps nothing and can be very harmful especially when repeatedly pushed to people who don't have the education to reject it.
Self-medicating is not intrinsically bad. Doing anything to yourself without doing your homework, and intelligently monitoring the effects of it over time is bad. Telling other to do things you saw on the interweb and some salesman said (or someone repeated without checking to find out where the suggestion originally came from) was good for you no matter what the science says is worse than bad, it is harmful to others.
Self-medicating is not intrinsically bad. Doing anything to yourself without doing your homework, and intelligently monitoring the effects of it over time is bad. Telling other to do things you saw on the interweb and some salesman said (or someone repeated without checking to find out where the suggestion originally came from) was good for you no matter what the science says is worse than bad, it is harmful to others.