If you can't speak frankly and candidly in your private, secret, and classified communications with the government you represent, how are you supposed to do your job? How do you give your government good information and an accurate assessment of the situation on the ground? If your impression of the President of Afghanistan is that he's corrupt and paranoid, your country needs to know.
Suggesting that we extend political correctness into classified communications is completely absurd. The expectation is that these documents will never see the light of day until they're only relevant in an historical context.