Your question seems to stem from the belief that discrimination is illegal, which it is not. Discrimination is completely legal, including in hiring practices,

Your question seems to stem from the belief that discrimination is illegal, which it is not. Discrimination is completely legal, including in hiring practices, as long as you're not discriminating against a protected class (either directly or by proxy). That's why the classes are explicitly enumerated, because if it's not in that list you can discriminate based on it. If you want to open a shop and put a sign out that says "No customers with blue eyes permitted" you're completely within your right to do so. But let's say you discriminated against some other form of eyes, that maybe disproportionately affected groups of a particular race or national origin, that would be illegal.