,,,
You're analysis seems to ignore that PC is not government mandated. Most PC "enforcement" is corporate self-censorship. It seems being insulting and nasty toward other people is bad for productivity.
What is most humorous is how the concept PC in right-wing lingo has grown from a social disdain for racist, sexist, and other ethnically nasty talk... to anything that liberals are normally against in speech.
Universities and corporations have rules against the derogatory language and nasty behavior that decrease productivity in both work and the sclassroom... and have no real academic or work-related purpose. Honestly... when has the need to call a black guy by some derogatory name, avow your hatred for gays, or call a girl a ***** ever been relevant to anything in classroom or work? Never. It's only disruptive.
You are however under no legal obligation to be PC in things you do for entertainment, when sending letters to a politician, or anything else for that matter in which you are not participating in a corporation or classroom.
The only thing that stops you is the disdain you will receive from others, up to and including the use of their own resources to bar you from media and disassociate from you.
There is no constitutional protection from the way people react to your speech.
I'm not entirely sure why anyone feels it is necessary to be rude, racist, mean, or whatever... and how it is they expect it to help their cause...
but no one is actually stopping you.
You can run out into the street and ramble on about Jews and blacks and women and whatever...
Just don't expect it's going to make people want to give you a job or be around you.