I feel compelled to clarify this: Hong Kong is part of China, and has been since 1997. Saying that Hong Kong is not part of China is like saying that Texas is not part of the United States because at one point they seceded. These days, Texas has no more right to secede from the US than Hong Kong from China, even if there are people in both territories who would prefer full independence. Consequently, to a Chinese person, hearing "I'm from Hong Kong, not China" would be like hearing "I'm from Texas, not the United States" as an American.
Granted, someone saying the latter should never be met with death threats, just like the former!
Granted, someone saying the latter should never be met with death threats, just like the former!