Gun ownership is a Constitutional right because it a fundamental human right.
But you may have a different view of what counts as fundamental human rights. And a representative of the Chinese Government would have an even different view.
One might even ask if fundamental human rights even exist, since they are constructs of societies and are relative between different societies.
YouTube Banning assembly videos is not "against the Second Amendment" at all. Your right to own a gun is not affected in any way by not being able to watch or post a video about assembling the gun. Worst case, you'll need to read (or write) a manual.
It's not even against the First Amendment, because that's only about the government suppressing political speech. Besides, the First Amendment only guarantees your right to speak; it doesn't guarantee that you'll have a platform to spread your speech, or that anyone will listen to you.
Other rights in the US Bill of Rights are more globally accepted as inalienable human rights in all/most jurisdictions.
And why would banning assembly videos on a private platform considered going against the 2nd amendment?