Not that this has any sort of connection to this issue, but I'll point something out to you.
The German legal system did not know what to charge the man with.
Meaning, you can't possibly legislate with every possibility in mind.
Of course it does. Your stated position is that anything two consenting adults wish to do in private is none of the government's business.
Two consenting adults decided to have one eat the other and record the event for the one's future memory. And you must believe that nobody should care.
Shalom.