Anti-discrimination laws exist because of the exceptionally well-documented tendency of people in positions of power to judge people based on their gender, sexuality, creed or the color of their skin.
I do understand that you think otherwise, I have met many people who see things differently.
The closest analogy I can find is the concept that commercial speech deserves less protection than private speech.
It is a matter of opinion and prevailing mores. In my opinion, becoming an employee is a voluntary decision (unlike, say, being drafted into a war), and should be treated the same as becoming a trade union member or a volunteer in a church organization.