It means "not politically correct", i.e. "politically incorrect". It basically means not to offend people when speaking. "Political correctness" is used pejoratively (i.e. in a negative sense) when it is thought to maintain a problematic status quo, discourage thinking, speaking, and action, and bowing down to made-up problems, but it can be positive in that it can be diplomatic, avoiding unnecessary conflict and ill-formed stereotypes, scapegoating, and can protect those without a voice.
According to the Merriam-Webster dictionary:
conforming to a belief that language and practices which could offend political sensibilities (as in matters of sex or race) should be eliminated
It was also a popular television program:
(which was basically continued as "Real Time with Bill Maher", which is an excellent show IMO)