Discrimination based on what a person can keep private is harder to define.
For example, Americans believe religious discrimination is wrong. So it would be wrong to fire someone because they are Jewish. Especially if they are government employees whose prayer rugs don't fit unseen in their work cubicle. Government regulations say federal employees should not place religious items in public areas or on walls where the public might see them and misconstrue them as placed there by the government, which cannot establish a national religion. Because government employees represent the government while at work.