Given that there’s a whole lot of “German historical artifacts” that are illegal it’s a logical extension from old symbols of hate and aggression to new.
Zorro is sad.
Makes logical sense, since it's almost equivalent to how the nazis used the swastika.
It's a bit of a dumb law though.
Interestingly, swastika has a similar history. The word means 'symbolizing well being' in Sanskrit. It still has the same meaning in Indic religions. Apparently, it had a similar meaning in Europe too, until the Nazis hijacked it for their cause.