In The Giver, what does it mean to be politically correct?

The citizens have to be very careful how they use language and never be impolite.

To be politically correct means that you do not offend someone.  In Jonas’s society, political correctness is an idea taken to the extreme.  No one is ever supposed to offend anyone, ever.  They try so hard to make sure that no one is ever uncomfortable that they have many strict rules governing people’s behavior.

The community values Sameness, and calling attention to differences is not allowed because it might make someone uncomfortable.  An example of this is when Lily comments on the fact that Jonas’s light colored eyes are different from most everyone else in the community.  Jonas expects her to be scolded for being rude.

No one mentioned such things; it was not a rule, but was considered rude to call attention to things that were unsettling or different about individuals. Lily, he decided, would have to learn that soon, or she would be called in for chastisement because of her insensitive chatter. (Ch. 3) 

In fact, in Jonas’s community anything that might be considered rude is outlawed.  You do not call attention to other people.  You do not call attention to yourself.  You don’t single anyone out, and if you do break any of these rules, you apologize immediately. 

Precision of language is the cornerstone of Sameness.  Children are taught from a young age that they need to be very precise and never say something that they do not mean.  For example, Jonas is scolded for saying that he is “starving.”  

To say "starving" was to speak a lie. An unintentioned lie, of course. But the reason for precision of language was to ensure that unintentional lies were never uttered. Did he understand that? they asked him. And he had. (Ch. 9) 

The goal is to make sure that everyone exists in a state of simple-mindedness.  There are no emotions.  As soon as someone has a feeling, it is quickly dismissed.  This is the purpose of the telling of feelings at night and the telling of dreams in the morning.  No one should ever be made uncomfortable.  That is how you keep your population in line.

Any uncomfortable information is kept from the people.  They have no sense of history.  Each person has his or own memory, but knows nothing about the past.  The community's history is maintained through intergenerational memories held by the Receiver of Memory.  That way, no one has to face anything disturbing.  The past simply doesn't exist.