Do judges have a duty to speak Mandarin in court?

Ultra-nationalist Peking University professor Kong Qingdong (孔庆东), who boasts of being a direct descendant of Confucius, stirred up a controversy the other day with televised insults to the people of Hong Kong - mocking their accent, calling them dogs (he later claimed he only meant some of them), and declaring that all Chinese had a duty to be able to speak Mandarin. (Here's a video of his remarks and the Hong Kong subway incident that prompted them.)

I want to look particularly at his claim that all Chinese have a duty to speak Mandarin. Here's what he said, in the original and in translation: "说普通话的人没有义务、没有必要掌握任何一种方言。中国人有义务说普通话。. . . 当你遇到一个人，他所操的方言跟你不一样的时候，怎么办？双方都应该说普通话。故意不说普通话是什么人？王八蛋！" ("People who speak Mandarin have no duty and no need to speak any other dialect. Chinese have a duty to speak Mandarin. . . . When you meet with someone and his dialect is different from yours, what should be done? Both parties should speak Mandarin. What kind of person would deliberately not speak Mandarin? A bastard!")

This is where Prof. Kong may get himself in trouble, and not just for his un-Confucian way of expressing himself, which would seem more suited to a Legalist book-burning. In the trial of Li QInghong (黎庆洪) just conducted in Guiyang, the presiding judge decided on the third day of proceedings to stop speaking in Mandarin and began instead to speak on in local Guiyang dialect, making it difficult for Li's lawyer to understand the proceedings. When Li's lawyer objected and said that the judge was required under relevant law to speak Mandarin, the judge said that it was his right to use Mandarin or Guiyang dialect as he pleased. But perhaps Prof. Kong will surprise me and denounce the presiding judge as a bastard.

Thanks for Flora Sapio for bringing this interesting aspect of the Li Qinghong case to my attention.