This recent New York Times article raises some interesting questions about the extent to which the law should dictate whether employers can discriminate on the basis of behavior outside the workplace. The article focuses on health care facilities that have banned smokers, but opponents argue that smoking differs little from other legal off site behaviors like engaging in risky sports, eating unhealthy food, drinking, and (by implication) unsafe sex. According to the article even one anti-smoking organization opposes this form of discrimination citing apparent socioeconomic differences between smokers and nonsmokers.
Employers apparently want to reduce absenteeism and health costs. Health care institutions also want to present an image of their employees as healthy, perhaps to enhance their image and set an example. The ban would also present an incentive for smokers to quit.
Employers could go further by banning fast food eaters, sky divers, drinkers, and people who don't use condoms. But eliminate enough categories of risk takers and you will not find sufficient qualified workers. Furthermore, employers will have to decide whether the costs of discovering such behaviors and firing high risk workers only to have to find low risk workers and train them makes business sense.
As for secondary discrimination by association, remember you're providing an incentive to better health, and continuing to smoke is a free choice.
I say let the employers decide. What do you think?