On which grounds? In some cases (I'm thinking of Germany), the ban on neo-Nazism speech IS in the Constitution, if I remember well.
Well I guess that makes it moral and just then. Because you would totally say the same thing if the DPRK constitution said certain types of speech were banned. It's okay because their Constitution banned it.
What part of protecting unpopular speech being a core part of any Democracy don't a lot of Europeans understand? You figure of all people they would understand. But I guess as long as they personally agree with the ban then it's cool. Tools.