Mar.20, 2014 | HANDBOOK OF INTL.DIPLOMACY
Handbook of International Diplomacy―The Authoritarian Edition: CRITICISM - Relativity of Misfortunes
Always remember that the misfortunes of others are (or can be construed to be) worse than your own.
Be prepared to ridicule adverserial foreign countries/people for problems/mishaps to deflect scrutiny from your own, much worse, track record. This test case of China critisizing France's air pollution, is a by-the-book initiative, succinct and effective.
[ I have no idea though why they are calling Paris "gay". Maybe they are old-school linguists, leafing through colonially bequeathed dictionaries, or have been reading too many UKIP "meteorological statements". ]