Political correctness: the avoidance, often considered as taken to extremes, of forms of expression or action that are perceived to exclude, marginalize, or insult groups of people who are socially disadvantaged or discriminated against.
Some people avoid expressing pro-life views for fear of being viewed as a misogynist; some people avoid labeling an incident an act of terrorism for fear of being viewed as an Islamophobe; some people avoid expressing traditional views on sexual morality for fear of being labeled a homophobe. These are but three examples reminding us that political correctness is all around us.
That said, Trump is attempting to use our aversion to “political correctness” to excuse his incivility. Not calling people “‘fat pigs,’ ‘dogs,’ ‘slobs,’ and ‘disgusting animals’” is not being “politically correct”; it is being a decent person.