The Chinese airline has every certain right to advise us on areas populated by blacks . As a Chinese student myself that used to study in London, I've been through rough areas, and certainly bumped into situations where groups of South-London speaking blacks will come up and start shouting stereotypical Asian racial slurs to me, regardless whether it is in the morning or at night. You might think that if the blacks come to China it will be similar, but no most blacks don't understand Mandarin, and racial slurs to them will most likely be brushed off as they wont feel anything what they are saying