The German constitution does not recognize freedom of speech; what it does recognize is freedom of political expression. There's a limit to this, though, when it is perceived to endanger public peace. Holocaust denial and suchlike has always been considered an assault on public peace. No public figure will be seen denying the holocaust or similar, the only purpose of that sort of statement can be to incite a mob. That's the background.

Now consider this: the German constitution was commissioned in 1948 by the Allied Powers, there was much experience in the Commission that developed it with constitutions of democratic nations, and the Nazi experience was fresh in everyone's mind. I think the fact that Germany does not have "freedom of speech" written in its constitution wants to tell you something.

TL;DR: Germany does not recognize freedom of speech. Germans consider this to be a Good Thing.