If we turn to nature as an example, do we have example of great apes, whales, dolphins having sex with father/mother etc? And if nature tells us it is all good to have sex with whatever, how come anthropophagy is a taboo between all consenting adults (if one
does not want to live anymore)
As I said the word "taboo" becomes meaningless from that german decision.
I wouldnt want to turn to nature for guidance for what should be legal. Murder, rape, theft, they're all found in abundance in the animal kingdom. What I want to have as a measuring stick is "how much damage/benefit does something do?". I the best way to legislate is to find an issue, answer that question, and propose a solution, measuring it with that same question.
What's illegal, immoral, unethical, and what's taboo are different groups that all overlap at different points. And it's every generation's challenge to figure out what should be in each of those categories.