It's a pertinent fact of the case and answers an obvious question most would have. After reading your proposed edit, since "that nation's secret police" is ment

It's a pertinent fact of the case and answers an obvious question most would have. After reading your proposed edit, since "that nation's secret police" is mentioned, the obvious question most would instinctively have is "what country are they talking about?" Reading the letter as a whole, it seems harassment and free speech was the main focus. "China" is mentioned once, and "Chinese" is mentioned once.