As an addendum, PC is also the *intersection* of discouraging certain speech and protected groups. So you can't have the latter without the former. If there are protected groups, and therefore consequences (legal, that you probably support, or social, that SJW's inflict) for crossing them, they can and will be used even if one is not crossing them; that's human nature.
So if a man gets promoted over a woman, in some cases the man will genuinely be the better performer, but the woman experiences the popular Dunning-Kruger Effect and sues. Or if a man says something to a woman at work and she takes it the wrong way, another lawsuit. So no one will want to work with people in these protected groups, out of fear. And organizations will be less likely to hire them in the first place.
So, the conclusions are:
1) If you support the notion of protected groupings of human beings, you also implicitly support muzzling speech, because that is necessarily one of the results.
2) Rather than make the situation worse, for *both* protected and unprotected groups, it is wisest and fairest to abandon this Left-wing cancer of an idea (that's designed to tear us apart) and to instead tell people tough titties*, there'll be no protected groups, you're on your own, adapt.
*Phrase chosen intentionally for its sexual (/sexist?) reference.