[Publius6961]

But a job is a privilege and not a right, unless you are in the protected classes. Any guesses as to the complexion of the fired employees?

Bingo!
The analyses here are right on, except for one tiny detail. The "protected" classes are arbitrary and capricious; to say nothing of absurd.

A 300-pound slob male can come to work as a woman and since the law "covers" him, it's OK.

I could live with a totally unrestricted right to work for someone, or not; and to employ someone, or not.

The analysis here applies simply to losers and the marginally competent. Where I work, I am sure if any smoker is singled out and fired, every smoker would quit.
Incidentally, the marginal employees, the chronicaly absentee and irresponsible are usually non-smokers. and female.

[tomkat]

..and female

[Modernman]

A 300-pound slob male can come to work as a woman and since the law "covers" him, it's OK.

Sexual orientation is a protected class in very few places. Most places, you could fire this guy on the spot.