Smoking is never a good idea, but if you live with others, it's not only a bad idea in relation to your own health, it's also selfish to expose others to all the toxins that smoking spreads. Of course, some people are fine with it and smoke themselves, and don't care about being exposed to it, but that doesn't make it any less unhealthy to them. I think people who live with others shouldn't be smoking in their homes if they care for others who live there.
For much of my childhood I've been exposed to smoke myself daily. It wasn't until I began reading about the health effects when I was around 15 that I refused to accept smoking inside the home. Those 15 years of involuntary exposure which could easily have been prevented are unforgiveable to me.
Just as an example... COPD, which is mainly caused by smoking, is the 4th biggest cause of death in humanity and to blame for 5% of deaths.
http://www.who.int/mediacentre/factsheets/fs315/en/Then there's the increased cancer risk, etc., etc.... But of course the tobacco companies making money off people's deaths and addictions won't be charged with genocide.