You are not owed clean air in public spaces. You are not owed air free of unpleasant smells. Your freedom ends where mine begins.
If you really care about unhealthy things you inhale, why aren't you spending your time ranting against car ownership? Emissions and tire wear produces magnitudes more harmful particles you inhale every day than being in the general vicinity of someone who smokes.
Naturally you could also ask a smoker to stand downwind from you at the bus stop, or even to not light up in the first place. But the smoker has just as much rights to the public space as you do.
If we try to regulate what smells you might encounter outside there are so. many. things I'd want gone as well because they make me feel sick to my stomach. Perfumes, foods, sweaty asses. Burps and farts.
I understand how annoying public smoking can be, I live essentially next to three bars. Not a weekend evening goes by without some fuckers smoking under my window, forcing me to close it.
But I still support their right to do so (see first paragraph).