Doing a close up of people's opinions reveals no one is fully politically correct, this means that political correctness is always a viable weapon to shut down debates via ad hominem.

Taboo "political correctness"... just for a moment. (This may be the first time I've ever used that particular LW locution.) Compare the accusations, "you are a hypocrite" and "you are politically incorrect". The first is common, the second nonexistent. Political correctness is never the explicit rationale for shutting someone out, in a way that hypocrisy can be, because hypocrisy is openly regarded as a negative trait.

So the immediate mechanism of a PC shutdown of debate will always be something other than the abstraction, "PC". Suppose you want to tell the world that women love jerks, blacks are dumber than whites, and democracy is bad. People may express horror, incredulity, outrage, or other emotions; they may dismiss you as being part of an evil movement, or they may say that every sensible person knows that those ideas were refuted long ago; they may employ any number of argumentative techniques or emotional appeals. What they won't do is say, "Sir, your propositions are politically incorrect and therefore clearly invalid, Q.E.D."

So saying "anyone can be targeted for political incorrectness" is like saying "anyone can be targeted for factual incorrectness". It's true but it's vacuous, because such criticisms always resolve into something more specific and that is the level at which they must be engaged. If someone complained that they were persistently shut out of political discussion because they were always being accused of factual incorrectness... well, either the allegations were false, in which case they might be rebutted, or they were true but irrelevant, in which case a defender can point out the irrelevance, or they were true and relevant, in which case shutting this person out of discussions might be the best thing to do.

It's much the same for people who are "targeted for being politically incorrect". The alleged universal vulnerability to accusations of political incorrectness is somewhat fictitious. The real basis or motive of such criticism is always something more specific, and either you can or can't overcome it, that's all.