That is Human nature and it's a evolutionary trait of survival. While in modern society we view it as disgusting that has been the Norm of our species from the dawn of time. Tribalism has reigned supreme in the effort to acquire and protect resources, family and friends. It even goes so far that when they brain map humans looking at people from other cultures, religions, and races in distress the Brain doesn't register the same volume of empathy. Even one study showed that the closer a person looks to yourself the more the brain will fire to show empathetic emotions.
Now with that said as humans we can override our instinct and use rational thought to tamp down those encoded traits.
But clearly some on this board have dark triad traits and feel justified in making sure their moral beliefs override the individual moral beliefs of the other side.