That's self-interest, not morality. A social convention that says I won't kill you if you won't kill me is based on self-interest and reciprocity. It does not define a system of objective and innate right and wrong.
Many human societies throughout history believed killing and conquest were totally justified and advanced the interests of their society.
Atheists are actually cultural Christians when you scratch beneath the surface. You adopt established religious values, without adopting the practice and ritual aspects of religion
You literally and unequivocally stated that humans are "just another animal".
But you don't call it 'murder' when a male bear destroys the cubs of a male rival. You don't call it 'rape' when a male deer forcibly copulates with a female deer.
