Specifically, you can't use pure existence of some acts in the nature as an excuse or confirmation for validity of any human acts.

Still studying the nature and the dynamics of living beings can actually help us humans more understanding our own actions, it gives us a good context as we're also animals, even if that thought isn't pleasing to everybody.

You’re presupposing a specific morality, and then rejecting other forms of morality on that basis. Alternatives are going to by definition be different. So, you need another way to judge them.