> I don't see why protected classes aren't an impartial standard? Admittedly, the inclusion of a particular class into the set of protected classes is perhaps a bit arbitrary, but it has the advantage of being simple while also addressing the common and egregious cases of injustice fairly well.

You're begging the question there. Unless there's an impartial standard for what constitutes a protected class, they're no more impartial than saying that people called Dave are allowed to break the law.