Is it legal for an employer to make a policy that only affects one person within that company?

That would depend on the policy. If one person rides a bike to work and they initiate a policy that says all bicycles have to be secured outside of the building rather than in, then yes, it would be a legitimate policy. For cyclists, that's actually a common problem. If the policy states that Fred the janitor can't bring his bicycle inside while all the guys in the accounting department do it, then there might be a problem.

it certainly could be. It would depend on the policy.

As an example, if there is a policy about beards and mustaches an there only happens to be one male employee, that policy would certainly be permissible

Why fight this battle get another job and work hard and this will be the former employers loss

Sure it is, unless it is a specific violation. You know like you say only this race.

depends... if the policy is not to smoke crack and only one guy is smoking crack I'd say it's fair.

Can you give an example?