This question was put to me by a sixteen year old boy from a Himalayan country about four years ago.
“I know the owner of a small shop. One day, the owner was busy when a customer who had bought a cigarette was looking for the lighter. I knew where the lighter was and went to get it for him but I was in two minds because by giving him the lighter I was helping the owner and the customer but, at the same time, I was helping the customer damage his health.
What should I have done?”
There are no shoulds, only possibilities, probabilities, and choice. Shoulds are anathema to freedom.
It seems that smoking is a risk factor for cancer.
Diet seems to be a much greater risk factor.
If you have a diet with lots of fresh fruits and veges, no spray residues, and you get reasonable exercise, you can smoke all you want and are unlikely to get cancer.
It is only on the common western diet of animal products, extracted fats and oils, refined foods with lots of added sugars and lots of introduced carcinogens, that smoking is really a problem.
I had a friend who died at 92, and smoked every day, but ate food from his own organic garden all his life – never had cancer.
In my own case, I was diagnosed terminal cancer, and after change of diet, am well out into the tail of the 1% survival curve, without any obvious signs of cancer.
In my case, I would give him the lighter, and ask about his diet.