Let me try and make it clearer for you: there are a lot activities that pose a serious threat to one's health other than the very demonized smoking habit. They can be job related, diet related, related to your location, physical activity, sexual habits, etc. These all are choices you have to make at one point or another. Indeed, you can always get another job, change your diet, where you live, exercise more, or engage in less dangerous sports, be more responsible with who you date, etc.
If you bar health insurance to smokers because they willingly harm themselves, then you should also do the same for all who you engage in risk activities. Speculator? No health insurance. The level of stress endured under your working conditions will put you at risk of heart problems by the time you're 40. Drinking too much soda? No health insurance. At risk of diabetes. You live next to a refinery? No health insurance. It's been proven homes next to oil industry facilities put you at risk of cancer. Enjoy surfing, rafting, mountain biking? No health insurance. These activities increase the risk of bone fracture drastically. Enjoy having multiple short-lasting relationship and engage in sexual activities with them? No health insurance. You put yourself at risk of STDs.
On top of that, what if a smoker gets hit by a drunk driver, needs rehabilitation to learn how to speak, eat and walk properly again but has no health insurance? How what happened is his fault and what are we punishing him for?
Are we talking about smokers' access to health insurance or second-hand smoking?