You're not adding any information when you post like this. It's just a strong opinion with a strong feeling attached. When someone else with the opposite opinion comes along and blasts their opposite feeling, no interesting information will be exchanged. Therefore it's off topic for thoughtful conversation, which is what we're trying for here.

An HN thread thrives on curiosity and specifics, withers on the gruel of grandiosity, and fries under scorching rhetoric.

The problem with bringing such links into arguments like this is that no one does so for reasons of intellectual interest. For example, in this case, people aren't actually interested in the plight of the Uighurs. Rather, it's convenient ammunition for justifying pre-existing political and national feelings. Such a move is not part of thoughtful conversation at all; it's just ideology and tribal loyalty, which explains why the discussions are so utterly repetitive—and therefore off topic for HN.