If China sent it as a statement to every newspaper and television channel in the US, do you think they should be required to run it as a story?
Twitter could just let the tweet exist for people who personally choose to follow the Chinese US embassy at no cost to other tweets. I mean, it's from a national government's embassy, their angle is not hidden at all.
Now they open themselves up to all sorts of questions, are they softer on the Saudis? On Israel?
Getting into picking and choosing which foreign governments are allowed to post, and which messages they'll countenance, at additional expenses for their mod team? Twitter has a foreign policy?