Most politics is off-topic for HN. Also, it typically leads to shouting matches, which are terrible discussions. It's not what HN aims for, and so political articles usually get flagged.

Arguably, this one is more on-topic than most politics. Also arguably, the discussion hasn't degenerated (yet). So, maybe flagged just because of politics, rather than because the discussion is awful.

By the way, flagging is done by users, not by the moderators. So it's us, not YC, that thinks this is problematic (or likely to become so).