This, if correctly publicized, would be the best motivation in getting huge amounts of people to stop. Think of a slogan like "Only the poor still smoke" or "it's what losers do" and how it would impact people. Suddenly you'd be embarrassed of being seen smoking.
I don't think so. You are correct that there are a large number of people who don't want the social stigma of being poor etc., but for many they see it as one of the few pleasures they can still have. To these people, they smoke, most of their friends and family smoke, and life is a struggle on a day to day basis. To them calling them a loser doesn't shame them, it just makes them more angry towards you.
This can be a powerful driver. And if it gets people to stop smoking, which is a devastatingly unhealthy habit, well, I'm ok with that.