It shouldn't be left to choice if people like, (I'm guessing you) refuse to stop, when people's health is at stake. Oh but I forgot passive smoking is a myth, even though I myself know 3 people who suffer from being in smoky rooms. I don't want shirt sniffers breathing in my smoke - I want segregation - a just and fair to all solution. Why would anyone oppose it? It works in Spain.
The argument is whether passive smoking kills billions of people every hour - not whether smoke aggravates asthma.
Segregation in office canteens and such like has existed for many years, there was one at my place of work and it never really worked too well. Could it be made to work? Probably, but why bother, when a complete ban will do more to help people kick the habit. I'm afraid this is one of the few areas where I quite rightly think that 'choice' as you put it should be removed because it may help people, like me, break the addiction. So I'm all for it.