What about WeChat censoring your speech, is 1st amendment okay with that?

"Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the Government for a redress of grievances."

Note the subject.

So yes, the First Amendment is okay with any censoring of information by a foreign government or company.

UN Universal Declaration of Human Rights:

"Article 19.

Everyone has the right to freedom of opinion and expression; this right includes freedom to hold opinions without interference and to seek, receive and impart information and ideas through any media and regardless of frontiers."

I don't see any mention of government there. Why limit the interpretation of free speech to the US constitution? How do you reconcile ideologically or philosophically that it is not ok for US Congress to limit speech but ok for other powerful entities?

> Why limit the interpretation of free speech to the US constitution?

Because that's literally what the grandparent asked. You appear to have a completely different question.

But they can't exercise the right with this tool.

Sure they can. They communicate using it. They have rights.