Actually, it's co-opted anti-communist language.

Soviet dissidents used the phrase to say when something was true, but not tolerable within the party's narrative and shouldn't be spoken out loud:

"It's correct, but it's not politically correct." Or alternatively the opposite: "It may not be true, but it's politically correct."

They took that a dissident term that lambasted their hypocrisy, and turned it into a concept that tries to denote "being kind".