TOKYO—Some of the world’s largest broadcasters including American network NBC are being asked by human rights groups to cancel plans to cover next year’s Winter Olympics in Beijing. The Winter Games are scheduled to open on Feb. 4. The request comes in an open letter from rights groups representing minorities in China, including Uyghurs, Tibetans, Hong Kong residents, and others. The letter, obtained by the Associated Press, was sent Tuesday to NBC Universal chief executive officer Jeff Shell and other international broadcast executives. NBC is paying $7.75 billion for the rights to the next six Olympics and works closely as a partner with the Switzerland-based International Olympic Committee. Those payments are estimated to account for up to 40 percent of the IOC’s total income. The letter says the broadcasters risk “being complicit” in the “worsening human rights abuses” in China. The letter comes just days after the delayed Summer Olympics …