Smoking 'smelling bad and making the environment unpleasant' is subjective.

Going back to your original post:

at the best case just smells bad and makes the environment unpleasant, even if its an open space.

So, I'm not interested in potential health hazards or similar, since those are your at worst arguments - you would still ban smoking even if it was at best, right? Besides, some people are allergic to some perfumes, and some things you lump in with 'smoking' (vaping, e.g.) has no 'secondary' effect, as far as I know - the 'smoke' is simply vapour that may be unpleasant, but is not harmful.

So, you're right: there is a 'logistical' issue with where the bar is drawn - but 'unpleasantness' is purely subjective, and the bar is highly variable.

So: would your view extend to other similarly 'unpleasant' things or not?