Smoking should be restricted in certain places so as not to harm others, and there has been significant progress in this regard, but banning smoking outright, especially when someone does it in private is not advisable. After all, we supposedly have freedoms in the United States and Canada, although they are eroding.
Do we ban everything that can possibly do harm? I find that watching CNN, with their biased reporting, is harmful to me; therefore I choose to avoid the channel, or take small does of it when I can tolerate their reporting. It's all about personal freedom and making wise choices. If I decided to start smoking I wouldn't smoke around those who would be adversely affected by it. I'd do it in private and would cherish the freedom to do so.