By David Ljunggren and Yew Lun Tian OTTAWA/BEIJING (Reuters) – Canada joined Australia, Britain and the United States in a diplomatic boycott of the Winter Olympics in Beijing on Wednesday, with China calling the boycotts “political posturing” and a smear campaign. The United States was the first to announce the boycott this week, saying on Monday its government officials would not attend February’s Beijing Olympics because of China’s human rights “atrocities”, weeks after talks aimed at easing tense relations between the world’s two largest economies. China on Tuesday said the United States w…