"PC" is a favorite tactic used to trivialize a statement of concern.  If one can successfully brand a statement as merely a manifestation of "political correctness", he or she can simply dismiss it and ignore being confronted about the behavior.  As you note, Mr. Trump and his supporters use this as the "default" defense when they're confronted.  It's a bit like putting your fingers in your ears as saying "na, na, na" as someone is saying something you don't like.  regards, Gary