> They were pretty happy to attack their own civilians, [...]

Yes.

> [...] I see no reason to think why that would be different abroad.

Well, you can look at the history of the PRC so far.

> I would imagine it isn't. See also: partnering with Putin in the war with Ukraine.

It's not all that much of a partnership. They are mostly squeezing Russia dry with cheap oil, and press territorial concessions out of the Tsar in the East, when he's busy in the West.