Even if I were to condone censorship, I do think that in any case announcements by the government are special. Trump's form may be off, it might not look official, but absent other more formal press releases etc., this is as official as it gets. And such announcements do need to reach the citizens of the affected nation/state/area, because they do directly influence people's lives, health, the society and the state. Any company censoring those better be damn sure that that censorship won't have any adverse effects on anyone...

On the other hand, if the announcement were too provocative/evil/illegal, there are ways in a democracy to hold the wrongdoer responsible. This is not Facebook's or any company's task.