There's politics, and there's politics. There's a difference between discussing whatever the US President blurted out on Twitter today, discussing whatever gaffe some local politician made, discussing which party is better and why, whether a group is pushing it too far, and then "abuses of human rights and freedom". The difference has a bit of "you'll know it when you see it" flavor to it. I think that in this light, he sees the issue of Hong Kong not as "politics", but as the real deal, an issue of more fundamental values and freedoms.
I've recently noticed that some people don't see the difference between "types" of politics. I don't understand why. To me, the difference has always been obvious. Some politics are about really important issues. Most of it is bullshit, just something that makes people with nothing better to do to jump at each other's throats. People have been creating "safe spaces" shielded from the latter for ages. The concept of not talking about the bullshit politics and religion at the dinner table is quite old.