Is it an "attack" on URMs to say that affirmative action is wrong?

Is it an "attack" on immigrants to approve of Republicans' immigration policy?

Is it an "attack" on women to say that a 20-25% representation of women in tech is an acceptable figure?

There are many places (the company at which I work, for one) where such statements genuinely are seen as attacks.

While it's true that abject denigration and truly extreme political views (I'm talking actual white nationalism, or nationalist socialism here not what is usually referred to by flippant usages of the word "Nazi") deserve to be socially rejected. In that sense political correctness is good. However, I think a substantial amount of what we PC advocates try to pass off as basic respect is constraining valid ideas. And that has the consequence of a handful of people thinking their views are the majority when they really aren't.

>being polite to a person or group the attacker dislikes"

If person A describes person B as homosexual" or "African American" instead of "gay" or "black" instead of in order to not offend person C who is straight and white is that an example of being polite or political correctness?

I would say the latter.

I think the language we'd use around person C depends on the context. "Gay" and "black" are fine to say at a bar but weird in a more formal setting like a courtroom or company-wide presentation. There's a ton of other language like this, nobody is upset that they can't tell fart jokes in a courtroom.