Your original contention was that only racists/sexists/whatever-ists hide behind "not a culture fit". That wasn't true. Now you seem to want to talk about some legal point. As I said, I don't want to discuss legality, that's some other topic.
Refusing to defend your statements is not a compelling way to win an argument.
If you believe that you can dismiss a candidate because you have "fundamental disagreements" about politics you are incorrect.
My contention is not that "culture fit" is used exclusively to bar candidates because of race/sex/etc, but that it is used in that way and that it is impossible to know what culture fit even means because it means different things to different people.
To some people, such as yourself, it means something that is not a valid reason to dismiss a candidate.
If nothing else, please respond to this question: If my company does not have a dress code, but the "culture" of the place is that everyone generally dresses in button down shirts and slacks every day. Furthermore, I believe fundamentally that people work more productively when they dress nicely, by my definition of what nice is, and that there is greater team cohesion when they do so.
Then a fully qualified candidate walks into my office wearing clean, but baggy jeans, a hat with a sticker on it, tilted to the side, sneakers, and a t-shirt. He actually mentions in the interview that his style is important to him and part of what defines him.
Can I dismiss this candidate on the grounds that he is not a culture fit for my organization?