You shouldn't do that.

Almost as if they think your choice is unconscious.

"Oh god! How did this smokeable get lit and in between my fingers!"

It may be a conscious clearing ticket to punch. In no other circumstance is it socially acceptable to look someone in the face and tell them that the choice they made is wrong.

I only hear it once per person. Their name has been cleared. What am I, a guilt factory? "Maybe if I had told that smoker that smoking is bad, they would have stopped." Who thinks that?

Update from the future: I used to smoke unfiltered hand rolled cigarettes in college. I was living with my dad, and it was a useful outlet. I slowed down, switched to vaping for years. (douche-flute, light-saber, robot dong, etc) (before it was cool) Since my partner had to quit, I quit in solidarity. It's hard. And you need to be able to self examine in order not to be a huge jerk. You have to be able to ascribe your clenched jaw to a chemical dependency, and not blame other people for how you feel. It's really hard.