I would argue yes, theoretically, more than 50% of a population could be non-conformist (although in a strictly literal sense, it's obviously a nonsense). I would say it depends on where the power lies - i.e. one can refuse to conform to the state and thus be non-conformist, but might be sharing a majority view.
Smoker's - unlikely I'd say. There's unlikely to be many, if any, millitant smokers - surely they're more likely to be libertarians?
Being in the closet isn't a reflection of being the minority, but of being (or a fear of being) persecuted, surely?