Well, that's the dirty little secret of freedom - you're responsible for yourself and ultimately you're on your own, up to the point you seek help and charity.
If you're not free to engage in risky behavior that may result in harm to yourself, you're not really free.
You'd be wrong; smokers don't cost the system more than non-smokers.
Common misconception. On the whole, the heavy smokers tend to die too young to cost as much as the non-smokers who live longer.
In any case, sin taxes are ultimately harmful to freedom. By supporting any sin tax, you are declaring that there's some arbitrary line where acts of self-harm deserve government intervention. Yesterday it was alcohol prohibition, today it's the drug war and sin taxes on smoking and alcohol, tomorrow it'll be high fructose corn syrup, the day after that it'll be something else.
One of the core tenets of libertarians (reasonable libertarians, not the childish anarchists who never grew up) is that government shouldn't be engaged in social engineering by offering monetary reward or punishment for "desirable" or "undesirable" individual behavior ... whether smoking, alcohol consumption, marriage (tax benefits), reproduction (child tax credit), home ownership (mortgage interest tax deduction), etc.
Moreover, sin taxes are inherently repressive, affecting the poor more than the wealthy. You would think that those on the Democrat / more liberal side of the aisle would have something to say about that, but they just can't get past their nanny state, paternalistic, "soft racism of low expectations", and earnest well-meaning need to protect the unwashed masses from themselves.