> They are not a protected class, but that doesn't mean you have to go out of your way to screw them over.

They've gone out of their way to screw themselves over; I see no particular reason to accommodate them. (Obvious exception for people who really do pre-date the widespread knowledge that cigarettes are both addictive and harmful, but that's a decreasing subset of smokers.)

> In your example, they could just move the smoking area, couldn't they?

Off campus, preferably. If you can't go eight hours without your drug of choice (especially one that harms the people around you when you use it), perhaps you have a bigger problem than an intentional lack of accommodations at your workplace.