The fundamental rights in the german constitution are interpreted in their broadest possible sense. All laws that restrict any of the fundamental rights can trace their root back to one of the other fundamental rights. They can't make it illegal to talk to your plants in the wrong tone.

Fundamentally speaking, this whole conflict is a conflict of two fundamental rights in the German constitution: Freedom of Speech (or Arts) and Human Dignity. The relevant laws can be traced back to those two rights.