I didn't read the parent post as justifying so much as explaining. Evolutionary or physiological explanations for behavior are useful in understanding the behavior. Some evolutionarily advantageous behaviors are morally positive, while some are morally negative (such as the examples you listed). With a proper understanding of the origins of desirable and undesirable behaviors (and, perhaps the reasons why they are considered desirable or undesirable), a society can better encourage and enforce the essential moral values that unite the society and allow it to function.