Just to clarify as I'm not sure I understand, so are you asking whether or not it should be illegal for a private business to segregate smokers from non-smokers? and in this case what exactly is the alternative that's proposed? Like is it a matter of private businesses should just let people smoke wherever they want in the place, that they should segregate them or not have them on the premises at all?
Sorry I'm just a little confused about the specifics of your question.
Though I will admit I don't have much sympathy for the idea of "smoker's right to smoke" and really don't understand why any one who smokes would try to claim such a thing exists when you consider how dangerous second hand smoke is. If we were talking like people who smoke marijuana I could certainly see that as that has readily proven medical benefits to the user and doesn't bring harm to those around them who may accidentally inhale it (at least not that I am aware of)
As such I will always question this idea of "smokers right to smoke". Why should someone have a right to do, in public, that which has been proven time and again to bring harm to those around him or her?