I'm going to guess this is more about Germany than it is about China In Germany, Nazi propaganda is illegal. This leaves Twitter with three options when dealing with a user who posts Nazi propaganda: 1. Leave it up, in violation of German law. 2. Delete the user's tweet, even though it is legal in most countries (and blocking it is a violation of the principle of free speech) 3. Block it only in Germany, and make it…
Blocking those tweets is not a violation of the principle of free speech. At least not in the legal sense. Private people and companies suppress speech all the time and that's fine. It's when your government does it that it's very wrong.
The difference between censored speech in Germany (or America: we have limits on free speech, too) and someplace like China is German society has agreed to limit certain offensive speech where as Chinese citizens don't really have a say in the matter.