China has labelled Prime Minister Scott Morrison joining social media app TikTok as a double standard. Mr Morrison has previously warned Australians about the Chinese-owned app and said it "connects right back to China", but he joined on Christmas Eve. Chinese foreign ministry spokesperson Zhao Lijian said Mr Morrison's choice of social media apps was "his own business", but added Australia should not discriminate against Chinese companies. "I need to reiterate that the Australian side should follow the principle of openness and market rules, stop abusing the concept of "national security" or applying double standard to serve its interests, and...