I don't agree with this. As in I agree with the generalization because in more than less times, its true. So should we descriminate against women who tend to take more sickdays over a career because of caring for kids, having kids? So should the elderly be descriminated against beause they take more sickdays to see the doctor, a debilitating immune system? I don't think so.
What if I'm a healthy smoker? Is it fair to hire someone with a health disease instead of me, a healthy smoker? In your argument that they shouldn't be forced to hire people that will cost them money, you're saying companies should be allowed to descriminate against people who will use their medical insurance more, who will take more sick days because of a disease. Thats not fair.
But lets make the example a choice, like you said. What about alcoholism? The difference is that smoking proves to show itself as a problem throughout someones life, where alcoholism only shows itself in a desctructive sense later on. So I might be a mild smoker and I will be descriminated against, but a full raging alcoholic with liver disease that will show up and cost the company money would be allowed to be hired while I would not be. What about people who do risky sports like bungee jumping, skydiving, diving? Its a risky sport, it could cause the company more money because they could die and retraining someone costs money. What about people who drive dangerously.
I think you're focusing on more visible examples of poor choice in peoples lives, like smoking, when people make horrible choices that could be detrimental to their health, their future and the companies future.
I say let people do what they like... if it makes you happy go take a walk while they smoke, go stroll around the block, noone said you had to sit there and work if you didn't smoke.
I didn't see this last bit... so obviously you understand the other point of view.