If we didn't have this idea that your ability to afford health insurance should be tied to full-time employment, then this shouldn't be an issue. But I can see that companies have a very good argument for discriminating against people who willingly choose to harm their bodies and incur higher healthcare costs. If we as a society don't want companies forcing their will on employees for things they do off-hours, then maybe we as a society should change the way healthcare insurance is handled.