I can totally imagine that situation, where you have to signal you are not interested in that conversation without coming across as rude. I had a first-generation Vietnamese colleague whose second ever sentence to me (in front of the entire staff) was "Taiwan, that is totally an independent country" - not even the caucasian Westerners had the balls to say that at any point. I told him "no comment" with a blank face, and he immediately looked totally scared.Unrelated to Taiwan but I had a similar experience with some HK colleagues at a previous job. I think they just assumed that I identified predominantly as American and thus was sympathetic to seeing China in a bad light so during the Umbrella Protests they basically talked freely about all sorts of resentments they had about Mainlanders like how Mainlanders pooped on the streets and hoarded all their milk powder, and were making their real estate expensive, aka Mainlanders are backwards and uncultured, while I just kind of kept my mouth shut and gently nodded to not start a fuss.
In the rare event when I do come across a compatriot - I mean a Taiwanese - we will always have the tact to basically avoid any China-related political conversation until we have ascertained bit by bit where each other stand. Taiwanese know this is a divisive topic between ourselves. But Westerners, no, they just don't get it.