You may have right to harm yourself by smoking (though I'm not sure!), but I don't think you have right to harm others by smoking in public places. The best solution might not be a blanket ban in all public places, but to allocate some "smoking" areas or cabins wherever possible. I don't know about other places much, but in Japan almost all restaurants have separate smoking and non-smoking tables, and most trains have at least one smoking car. But public buses are usually non-smoking.