What does the term politically correct mean?

Washington, D C
2120-September 1, 1945
To: D A MacArthur/C H Nimitz
From: H S Truman
   
"Political Correctness is a doctrine, recently fostered by a
delusional, illogical minority, and promoted by a sick mainstream media,
which holds forth the proposition that it is entirely possible to pick up a
turd by the clean end!"