Except by your own argument it really is. The UK has blocked many sites for many reasons. However, none of those reasons are for crowd control. Your example is ironically proof of the statement. This is the first time a western nation has banned media for the explicit purpose of quelling a protest and suppressing speech. Your example is a government banning a site not to quell a protest or to suppress speech, but instead because of a governmental disagreement between two nations. Now which one you think is valid for suppressing speech is a totally different question, only that they are two separate and completely different reasons.