The difference between poison and medicine is literally in the dosage. Anything can be a poison if too much of it is flowing in your blood stream or inhabiting your mass, some things just require far too much of a concentration to be quoted as a poison.
As for the cigarette, I refuse to believe this world has never had people burn some leaves to inhale the smoke. Unless the goddess has order these people be hunted down and purge, it's bullshit to whine about a guy grabbing some smokes. If you're going to allow alcohol to exist, you have no business talking about poison.
...Sorry, that just felt like a ridiculous term and condition to the ability.