I don't understand why every single discussion about China has to touch this issue and this is the first thing people do when they visit China.

Do you talk to Germans by starting off discussing how Hitler killed millions of people? Do you talk to Japanese people about WW2 and how was the experience being bombed by nukes after saying hello? Do you expect non-US citizens to start talking to you about the massacres of indigenous peoples of the Americas during the first meeting?

You don't go to a country just to re-visit their dark history. Regardless of how bad the censorship is, that is just rude behavior. Show some respect first, if you are really interested, make friends with them, then talk about it, they'd be happy to discuss it with a friend but not a stranger.