Appeal to nature
This equation is generally regarded as a fallacy for the following reasons:
- Civilization is inherently "unnatural", and any argument not based solely on force depends on the existence of civilized discourse, itself based on the principles of rational thought and analysis. When these are suspended or removed, society reverts to feudalism and only stops there due to the innate cleverness of human beings at manipulating each other with threats.
- The large number of obvious counterexamples. You wouldn't, say, defend a shark's right to attack swimmers (much less a vicious dog's right to maim children) just because that was its natural tendency, or make laws requiring that people behave more like chimpanzees.
As with many fallacies, there is a grain of validity to it – in this case, the fact that if something is done in nature, it may be somehow vital to survival, otherwise known as the argument from survival.