A good example of political correctness is the party line on Joss Whedon shifting over time.
One can try and stay ahead of the curve, hence the stern admonitions about the new Doctor Who being problematic because the lady is white.
But one can be politically incorrect by being too far ahead of the curve; much like trading the market one must be careful not to be too early or too late.
The trick is to never show enthusiasm for anything until you know whether it is problematic or not.
And be prepared to instantly disavow or recontextualise past opinions every time the winds shift; for this is in fact what political correctness means.
Political Correctness Limit Hypothesis: For any given item X, the odds of being declared problematic approach 1 as the time t goes to infinity.